Prepreg and carbon fiber reinforced composite materials

ABSTRACT

A prepreg containing a carbon fiber [A] and a thermosetting resin [B], and in addition, satisfying at least one of the following (1) and (2).
     (1) a thermoplastic resin particle or fiber [C] and a conductive particle or fiber [D] are contained, and weight ratio expressed by [compounding amount of [C] (parts by weight)]/[compounding amount of [D] (parts by weight)] is 1 to 1000.   (2) a conductive particle or fiber of which thermoplastic resin nucleus or core is coated with a conductive substance [E] is contained.

CROSS REFERENCE WITH PCT APP

The present application is a 37 C.F.R. §1.53(b) divisional of, andclaims priority to, U.S. application Ser. No. 12/376,763, filed Feb. 6,2009. application Ser. No. 12/376,763 is the national phase under 35U.S.C. §371 of International Application No. PCT/JP2007/065390, filed onAug. 7, 2007. Priority is also claimed to Japanese Application No.2006-214398 filed on Aug. 7, 2006; Japanese Application No. 2006-312531filed on Nov. 20, 2006; and Japanese Application No. 2007-038974 filedon Feb. 20, 2007. The entire contents of each of these applications ishereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a prepreg and carbon fiber reinforcedcomposite material having an excellent impact resistance andconductivity together.

BACKGROUND ART

Carbon fiber reinforced composite materials are useful since they areexcellent in strength, stiffness, conductivity, etc., and widely usedfor an aircraft structural member, a windmill wing, an automotive outerpanel and computer uses such as an IC tray or a housing of notebookcomputer and their needs are increasing year by year.

The carbon fiber reinforced composite material is generally aninhomogeneous material obtained by molding a prepreg of which essentialconstituting elements are a carbon fiber which is a reinforcing fiberand a matrix resin, and accordingly, there is a big difference betweenphysical properties of arranging direction of the reinforcing fiber andphysical properties of other direction. For example, it is known that animpact resistance expressed by a resistance to drop impact is, since itis determined by delamination strength which is quantitatively measuredas interlayer edge peel strength, not resulted in a drastic improvementonly by increasing strength of the reinforcing fiber. In particular,carbon fiber reinforced composite materials of which matrix resin is athermosetting resin has, in reflection of a low toughness of the matrixresin, a property to be broken easily by a stress from other than thearranging direction of the reinforcing fiber. Accordingly, various meansare proposed for the purpose of improving physical properties ofcomposite material capable of resisting to the stress from other thanthe arranging direction of the reinforcing fiber.

As one of them, a prepreg provided with a resin layer, in which resinparticles are dispersed, on surface region of the prepreg is proposed.For example, a method for providing a high toughness composite materialexcellent in heat resistance, by using a prepreg provided with a resinlayer in which particles consisting of a thermoplastic resin such asnylon are dispersed in surface region of the prepreg, is proposed (referto Patent reference 1). And, other than that, a method for developing ahigh toughness of composite material by a combination of a matrix resinof which toughness is improved by adding a polysulfone oligomer and aparticle consisting of a thermosetting resin is proposed (refer toPatent reference 2). However, these methods give a high impactresistance to carbon fiber reinforced composite material on one hand,but on the other hand, result in producing a resin layer to become aninsulating layer in the interlayer. Accordingly, there is a defect thatthe conductivity in thickness direction, among conductivities which areone of characteristics of the carbon fiber reinforced compositematerial, significantly decreases, and it was difficult to make anexcellent impact resistance and conductivity compatible in the carbonfiber reinforced composite material.

Furthermore, as methods for improving conductivity of the interlayer, amethod of compounding a metal particle to a matrix resin of carbon fiberreinforced composite material (refer to Patent reference 3), or a methodof compounding a carbon particle (refer to Patent reference 4) can beconsidered, but in these references, no reference is made to acompatibility of an excellent impact resistance and conductivity.

-   [Patent reference 1] specification of U.S. Pat. No. 5,028,478-   [Patent reference 2] JP-H3-26750A-   [Patent reference 3] JP-H6-344519A-   [Patent reference 4] JP-H8-34864A

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In such a circumstance, the purpose of the present invention is toprovide a prepreg and carbon fiber reinforced composite material havingan excellent impact resistance and conductivity in thickness directiontogether.

Means for Solving the Problems

The prepreg of the present invention has the following constitution toachieve the above-mentioned purpose. That is, a prepreg containing acarbon fiber [A] and a thermosetting resin [B] and in addition,satisfying at least any one of the following (1) and (2).

(1) A thermoplastic resin particle or fiber [C] and a conductiveparticle or fiber [D] are contained, and a weight ratio expressed by[compounding amount of [C] (parts by weight)]/[compounding amount of [D](parts by weight)] is 1 to 1000.

(2) A conductive particle or fiber of which thermoplastic resin nucleusor core is coated with a conductive substance [E] is contained.

Furthermore, the carbon fiber reinforced composite material of thepresent invention has the following constitution to achieve theabove-mentioned purpose. That is, a carbon fiber reinforced compositematerial containing a carbon fiber [A] and a thermosetting resin [B] andin addition, satisfying at least any one of the following (1) and (2).

(1) A thermoplastic resin particle or fiber [C] and conductive particleor fiber [D] are contained, and a weight ratio expressed by [compoundingamount of [C] (parts by weight)]/[compounding amount of [D] (parts byweight)] is 1 to 1000.

(2) A conductive particle or fiber of which thermoplastic resin nucleusor core is coated with a conductive substance [E] is contained.

Effect of the Invention

By the present invention, it is possible to obtain a carbon fiberreinforced composite material having an excellent impact resistance andconductivity together. By conventional arts, only a carbon fiberreinforced composite material which is low in conductivity when itsimpact resistance is high or which is low in impact resistance when itsconductivity is high, but by the present invention, it became possibleto provide a carbon fiber reinforced composite material simultaneouslysatisfying the impact resistance and the conductivity.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 An example of cross-sectional view of a representative prepreg.

FIG. 2 A graph which shows compressive strength after impact and volumeresistivity in relation to the weight ratio expressed by [compoundingamount of [C] (parts by weight)]/[compounding amount of [D] (parts byweight)].

EXPLANATION OF REFERENCES

-   -   1: carbon fiber layer (intralayer)    -   2: inter-formative layer (interlayer)    -   3: thermoplastic resin particle    -   4: conductive particle    -   5: carbon fiber    -   6: thermosetting resin

BEST MODE FOR CARRYING OUT THE INVENTION

The inventors surprisingly found that, as a result of investigating hardon conductivity mechanism in thickness direction of a carbon fiberreinforced composite material consisting of a carbon fiber and athermosetting resin, a carbon fiber reinforced composite material havingin a high level an excellent impact resistance and conductivity togethercan be obtained without decreasing carbon fiber content by, in additionto the thermoplastic resin particle or fiber which imparts a high impactresistance to the interlayer part on one hand but results in producing aresin layer to become an insulating layer in the interlayer, furthercompounding a conductive particle or fiber in a specified weight ratio,or compounding a conductive particle or fiber of which thermoplasticresin nucleus or core is coated with a conductive substance in theinterlayer part, and conceived a prepreg capable of obtaining such acarbon fiber reinforced composite material.

Prepreg is an intermediate base material for molding made byimpregnating with a matrix resin to a reinforcing fiber, and in thepresent invention, carbon fiber is used as the reinforcing fiber and athermosetting resin is used as the matrix resin. In such a prepreg, thethermosetting resin is in an uncured state, and by laying-up the prepregand by curing, a carbon fiber reinforced composite material is obtained.As a matter of course, even by curing a single layer prepreg, a carbonfiber reinforced composite material can be obtained. In a carbon fiberreinforced composite material obtained by laying-up a plural of prepregsand by curing, a surface portion of the prepreg becomes to an interlayerpart of the carbon fiber reinforced composite material and an inner partof the prepregs become to an intralayer part of the carbon fiberreinforced composite material.

The prepreg of the present invention is a prepreg containing the carbonfiber [A] and the thermosetting resin [B] and in addition, satisfying atleast any one of the following (1) and (2).

(1) A thermoplastic resin particle or fiber [C] and a conductiveparticle or fiber [D] are contained, and a weight ratio expressed by[compounding amount of [C] (parts by weight)]/[compounding amount of [D](parts by weight)] is 1 to 1000.

(2) A conductive particle or fiber of which thermoplastic resin nucleusor core is coated with a conductive substance [E] is contained.

In an embodiment satisfying the item (1), the prepreg or the carbonfiber reinforced composite material obtainable from the prepreg containsthe carbon fiber [A], the thermosetting resin [B], the thermoplasticresin particle or fiber [C] and the conductive particle or fiber [D]. Inthis embodiment, it is preferable to use a thermoplastic resin particleas the [C] and a conductive particle as the [D]. It is because a casewhere both of the [C] and the [D] are made into particle configurationis, compared to a case where one of them is in fiber configuration orboth of them are in fiber configuration, better in flow characteristicsof the thermosetting resin and excellent in impregnating property to thecarbon fiber. And, by using the thermoplastic resin particle and theconductive particle in combination, when a drop impact (or a localizedimpact) is added to the carbon fiber reinforced composite material,since an interlayer delamination caused by the localized impact isreduced, in case where a stress is loaded to the carbon fiber reinforcedcomposite material after such an impact, delamination parts generated bythe above-mentioned localized impact which would be starting points ofbreakage by stress concentration are not many, and since a probabilityof contact of the conductive particle with the carbon fiber in thelaminate layer is high to make it easy to form a conductive path, acarbon fiber reinforced composite material which exhibits a high impactresistance and conductivity cay be obtained.

On the other hand, in an embodiment satisfying the item (2), the prepregor the carbon fiber reinforced composite material obtainable from theprepreg contains the carbon fiber [A], the thermosetting resin [B] andthe conductive particle of which thermoplastic resin nucleus is coatedwith a conductive substance or the conductive fiber of which core ofthermoplastic resin is coated with a conductive substance [E]. Here, the[E] is, among the above-mentioned [D], that having a specific embodimentwhere a conductive particle of which thermoplastic resin nucleus iscoated with a conductive substance or where a conductive fiber of whichcore of thermoplastic resin is coated with a conductive substance. Byusing the [E] having such a specific embodiment, the effect obtained byusing the above-mentioned [C] and the [D] in combination, can beobtained only by the [E].

The embodiment satisfying the item (1) is, compared to the embodimentsatisfying the item (2), due to an effect of excellent toughness by thethermoplastic resin particle or fiber [D] in the interlayer part, it isexcellent in viewpoint that a delamination strength is high and animpact resistance is still high when a drop impact is added to thecarbon fiber reinforced composite material. On the other hand, theembodiment satisfying the item (2) is, compared to the embodimentsatisfying the item (1), since components to be used are not many,excellent in viewpoint of expectation of cost reduction and productivityimprovement.

It is preferable that the carbon fiber [A] used in the present inventionis, in view of exhibiting a higher conductivity, a carbon fiber having atensile modulus of at least 260 GPa, but in view of compatibility withthe impact resistance, it is preferable to be a carbon fiber having atensile modulus of at most 440 GPa. In view of such a point, it isespecially preferable that the tensile modulus is in the range of 280 to400 GPa, since conductivity and impact resistance can be compatible at ahigh level.

In addition, in view of impact resistance, since it is possible toobtain a composite material excellent in impact resistance and having ahigh stiffness and mechanical strength, it is preferable to be ahigh-strength high-elongation carbon fiber of which tensile strength is4.4 to 6.5 GPa and tensile strain is 1.7 to 2.3%. Accordingly, in viewof compatibility of conductivity and impact resistance, a carbon fiberhaving all characteristics of a tensile modulus of at least 280 GPa, atensile strength of at least 4.4 GPa and a tensile strain of at least1.7% is most appropriate. The tensile modulus, the tensile strength andthe tensile strain can be determined by the strand tensile testdescribed in JIS R7601-1986.

The thermosetting resin [B] used in the present invention is notespecially limited, as far as it is a resin capable of forming athree-dimensional cross-linked structure at least partially byprogressing a cross-linking reaction by heat. As such a thermosettingresin, for example, an unsaturated polyester resin, a vinyl ester resin,an epoxy resin, a benzoxazine resin, a phenol resin, anurea-formaldehyde resin, a melamine formaldehyde resin and a polyimideresin, etc., are mentioned, and denaturations thereof and resins inwhich 2 kinds or more of them are blended can also be used. And, thesethermosetting resins may be self-curable by heat or a hardener or acuring accelerator or the like may be compounded therein.

Among these thermosetting resins, epoxy resin excellent in a balance ofheat resistance, mechanical characteristics and adhesion with carbonfiber is preferably used. In particular, amines, phenols or an epoxyresin of which precursor is a compound having a carbon-carbon doublebond are preferably used. Concretely, as glycidyl amine type epoxyresins of which precursor is an amine,tetraglycidyldiaminodiphenylmethane, triglycidyl-p-aminophenol andvarious isomers of triglycidylaminocresol are mentioned.Tetraglycidyldiaminodiphenyl methane is preferable as a resin forcomposite material of aircraft structural material since it is excellentin heat resistance.

Furthermore, as a thermosetting resin, a glycidyl ether type epoxy resinof which precursor is phenol is also preferably used. As such epoxyresins, bisphenol A type epoxy resin, bisphenol F type epoxy resin,bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresolnovolac type epoxy resin and resorcinol type epoxy resin are mentioned.

Since a bisphenol A type epoxy resin, bisphenol F type epoxy resin andresorcinol type epoxy resin of liquid state are low in viscosity, it ispreferable to use them with other epoxy resin in combination.

Furthermore, since a bisphenol A type epoxy resin which is solid at roomtemperature (about 25° C.) gives a cured resin of a structure of lowercross-linking density compared to a bisphenol A type epoxy resin whichis liquid at room temperature (about 25° C.), said cured resin becomeslower in heat resistance, but becomes higher in toughness, andaccordingly, it preferably is used in combination with a glycidyl aminetype epoxy resin, a liquid bisphenol A type epoxy resin or a bisphenol Ftype epoxy resin.

An epoxy resin having a naphthalene skeleton gives a cured resin of lowwater absorption, and in addition, of high heat resistance. And, abiphenyl type epoxy resin, a dicyclopentadiene type epoxy resin, aphenolaralkyl type epoxy resin and a diphenylfluorene type epoxy resinalso give cured resins of low water absorption, and are preferably used.

A urethane modified epoxy resin and an isocyanate modified epoxy resingive cured resins high in fracture toughness and strain, and they arepreferably used.

These epoxy resins may be used singly or may be used by compoundingappropriately. It is preferable to use them by compounding with at leasta difunctional epoxy resin and an epoxy resin of trifunctional or more,since resin flowability and heat resistance after curing can be madecompatible. In particular, a combination of a glycidyl amine type epoxyand a glycidyl ether type epoxy makes it possible that heat resistanceand water resistance are compatible. And, compounding at least an epoxyresin which is liquid at room temperature and an epoxy resin which issolid at room temperature is effective to make tackiness properties anddraping properties of prepreg appropriate.

The phenol novolac type epoxy resin or cresol novolac epoxy resin givesa cured resin excellent in heat resistance and water resistance, sincethey are excellent in heat resistance and low in water absorption. Byusing these phenol novolac type epoxy resin or cresol novolac epoxyresin, it is possible to control tackiness properties and drapingproperties of prepreg while improving heat resistance and waterresistance.

As a hardener of the epoxy resin, it can be used if it is a compoundhaving an active group capable of reacting with the epoxy group. As thehardener, a compound having amino group, acid anhydride group or azidogroup is suitable. As the hardener, more concretely, for example,dicyandiamide, diaminodiphenyl methane or various isomers ofdiaminodiphenyl sulfone, aminobenzoic acid esters, various acidanhydrides, a phenol novolac resin, a cresol novolac resin, a polyphenol compound, an imidazole derivative, an aliphatic amine,tetramethylguanidine, a thiourea addition amine, carboxylic acidanhydrides such as methylhexahydrophthalic acid anhydride, a carboxylichydrazide, a carboxylic amide, a poly mercaptan and Lewis acid complexessuch as BF₃ ethylamine complex, etc., are mentioned. These hardeners maybe used alone or in combination.

By using an aromatic diamine as a hardener, a cured resin excellent inheat resistance can be obtained. In particular, various isomers ofdiaminodiphenyl sulfone are most appropriate for obtaining a cured resinexcellent in heat resistance. As to an amount of addition of thearomatic diamine as a hardener, it is preferable to add instoichiometrically equivalent amount, but in certain circumstances, forexample, by using approximately 0.7 to 0.8 to the equivalent amount, ahigh modulus cured resin can be obtained.

Furthermore, by using a combination of dicyandiamide with a ureacompound, for example, with 3,4-dichlorophenyl-1,1-dimethylurea, or byusing an imidazole as a hardener, a high heat resistance and waterresistance are achieved, even though being cured at a relatively lowtemperature. A curing by using an acid anhydride gives, compared to acuring by an amine compound, a cured resin of lower water absorption.Other than that, by using a latent hardener of them, for example, amicroencapsulated hardener, storage stability of the prepreg is improvedand, especially, tackiness properties or draping properties hardlychange even when being left at room temperature.

Furthermore, it is also possible to compound these epoxy resin andhardener, or a prereaction product of a part of them in the composition.This method is effective for viscosity control or improvement of storagestability in some cases.

It is also preferable to use by mixing and dissolving a thermoplasticresin into the above-mentioned thermosetting resin. As suchthermoplastic resins, in general, it is preferable to be a thermoplasticresin having, in the main chain, a bond selected from carbon-carbonbond, amide bond, imide bond, ester bond, ether bond, carbonate bond,urethane bond, thioether bond, sulfone bond and carbonyl bond, but across-linked structure may partially be contained. And, it may havecrystallinity or may be amorphous. In particular, it is preferable thatat least 1 kind resin selected from the group consisting of a polyamide,a polycarbonate, a polyacetal, polyphenyleneoxide, poly phenylenesulfide, a polyarylate, a polyester, a polyamideimide, a polyimide, apolyetherimide, a polyimide having phenyltrimethylindane structure, apolysulfone, a polyethersulfone, a polyetherketone, apolyetheretherketone, a polyaramid, a polyethernitrile and apolybenzimidazole is mixed and dissolved into the thermosetting resin.

As such thermoplastic resins, a commercially available polymer may beused, or a so-called oligomer of which molecular weight is lower thanthe commercially available polymer may be used. As the oligomer, anoligomer having, on its end or in molecular chain, a functional groupcapable of reacting with the thermosetting resin is preferable.

In case where a mixture of the thermosetting resin and the thermoplasticresin is used, a better result is obtained than a case where they areused alone.

Brittleness of the thermosetting resin is covered by toughness of thethermoplastic resin, and in addition, difficulty of molding of thethermoplastic resin is covered by the thermosetting resin, and a baseresin in good balance is obtained. A using ratio (parts by weight) ofthe thermosetting resin and the thermoplastic resin is, in view of thebalance, preferably in the range of 100:2 to 100:50, and morepreferably, in the range of 100:5 to 100:35.

Furthermore, in the above-mentioned thermosetting resin, for the purposeof improving conductivity of the carbon fiber reinforced compositematerial by increasing contact probability of the carbon fiber with eachother, it is preferable to use by mixing a conductive filler. As suchconductive fillers, a carbon black, a carbon nanotube, a vapor-growncarbon fiber (VGCF), a fullerene, a metal nanoparticle, etc., arementioned, and they may be used alone or in combination. Among them, acarbon black which is cheap and high in effect is preferably used, andas such carbon blacks, for example, a furnace black, an acetylene black,a thermal black, a channel black, a ketjen black, etc., can be used, anda carbon black in which 2 kinds or more of them are blended is alsopreferably used. The conductive filler mentioned here is a conductiveparticle or fiber having an average diameter smaller (generally 0.1times or less) than the average diameters of the conductive particle orfiber [D] and a conductive particle or fiber of which thermoplasticresin nucleus or core is coated with a conductive substance [E].

In an embodiment satisfying the item (1) of the present invention, sincethe thermoplastic resin particle or fiber [C] is used as an essentialcomponent, an excellent impact resistance can be realized. As materialsfor the thermoplastic resin particle or fiber [C] of the presentinvention, the same materials as the various thermoplastic resinsabove-exemplified as the thermoplastic resins to be used by mixing anddissolving into the thermosetting resin can be used. Among them,polyamide which can greatly improve impact resistance by its excellenttoughness is most preferable. Among the polyamides, Nylon 12, nylon 11or nylon 6/12 copolymer are preferable, since they are especially goodin adhesion strength with the thermosetting resin [B], and delaminationstrength of the carbon fiber reinforced composite material at the timeof drop impact is high, and effect of impact resistance improvement ishigh.

In case where a thermoplastic resin particle is used as the [C], as thethermoplastic resin particle shape, spherical, nonspherical, porous,spicular, whisker-like or flaky shape may also be acceptable, butspherical shape is preferable since it is excellent in impregnatingproperty to carbon fibers because it does not lower flow ability of thethermosetting resin, or since an interlayer delamination, generated by alocalized impact when a drop impact (or localized impact) is added tothe carbon fiber reinforced composite material, is more reduced, and thedelamination parts, caused by the above-mentioned localized impact,which are starting points of breakage by stress concentration in casewhere a stress is added to the carbon fiber reinforced compositematerial, are not many, and a carbon fiber reinforced composite materialwhich realizes a high impact resistance can be obtained.

In case where a thermoplastic resin fiber is used as the [C], as a shapeof the thermoplastic resin fiber, both of short fiber or long fiber canbe used. In case of short fiber, a method in which short fibers are usedin the same way as particles as shown in JP-O₂-69566A, or a method inwhich short fibers are used after processed into a mat is possible. Incase of long fiber, a method in which long fibers are arranged inparallel on a prepreg surface as shown in JP-04-292634A, or a method inwhich they are arranged randomly as shown in WO94/016003 is possible.Furthermore, it can be used after processed into sheet-like basematerials such as a woven fabric as shown in JP-H02-32843A, a non-wovenfabric as shown in WO94016003A, or a knitted fabric. And, a short fiberchip, a chopped strand, a milled fiber, or a method in which shortfibers are made into a spun yarn and arranged in parallel or random, orprocessed into a woven fabric or a knitted fabric can also be employed.

In the present invention, in case where a conductive particle is used asthe [D], the conductive particle may be at least a particle which actsas an electrically good conductor, and it is not limited to thoseconsisting only of a conductor. Preferably, it is a particle of whichvolume resistivity is 10 to 10⁻⁹ Ωcm, more preferably 1 to 10⁻⁹ Ωcm andstill more preferably 10⁻¹ to 10⁻⁹ Ωcm. When the volume resistivity istoo high, in the carbon fiber reinforced composite material, asufficient conductivity may not be obtained. As the conductiveparticles, for example, a metal particle, conductive polymer particlessuch as polyacetylene particle, polyaniline particle, polypyrroleparticle, polythiophene particle, polyisothianaphthene particle orpolyethylenedihydroxythiophene particle, or a carbon particle, and otherthan that, a particle of which nucleus of inorganic material is coatedwith a conductive substance or a particle of which nucleus of organicmaterial is coated with a conductive substance can be used. Among them,since they exhibit a high conductivity and stability, the carbonparticle, the particle of which nucleus of inorganic material is coatedwith a conductive substance or the particle of which nucleus of organicmaterial is coated with a conductive substance are especially preferablyused.

In particular, like the embodiment satisfying the item (2) of thepresent invention which is mentioned later, when a thermoplastic resinis used as the organic material and the particle of which thermoplasticresin nucleus is coated with a conductive substance is used, it ispreferable since a still more excellent impact resistance can berealized in the carbon fiber reinforced composite material to beobtained.

In case where a conductive fiber is used as the [D] in the presentinvention, the conductive fiber may be at least a fiber which acts as anelectrically good conductor, and it is not limited to those consistingonly of a conductor. Preferably, it is a fiber of which volumeresistivity is 10 to 10⁻⁹ Ωcm, more preferably 1 to 10⁻⁹ Ωcm, and stillmore preferably 10⁻¹ to 10⁻⁹Ω. When the volume resistivity is too high,a sufficient conductivity may not be obtained in the carbon fiberreinforced composite material. As the conductive fiber, for example, ametal fiber, a carbon fiber, a fiber of which core of inorganic materialis coated with a conductive substance or a fiber of which core oforganic material is coated with a conductive substance, etc., can beused. In particular, like the embodiment satisfying the item (2) of thepresent invention which is mentioned later, when a thermoplastic resinis used as the organic material, and a fiber of which core ofthermoplastic resin is coated with a conductive substance is used, astill more excellent impact resistance can be realized in the carbonfiber reinforced composite material to be obtained.

As to the volume resistivity mentioned here, a sample is set to acylindrical cell having 4 probe electrode, thickness and resistivityvalue of the sample are measured in the condition in which a pressure of60 MPa is added to the sample, and a value calculated from them is takenas the volume resistivity.

In the conductive particle or fiber [D] of the type coated with theconductive substance, the conductive particle or fiber is constitutedwith the inorganic material or organic material which is the nucleus orcore and the conductive layer consisting of the conductive substance,and as desired, an adhesive layer which is mentioned later may beprovided between the nucleus or core and the conductive layer.

In the conductive particle or fiber [D] of the type coated with theconductive substance, as the inorganic material to be used as thenucleus or core, an inorganic oxide, an inorganic-organic complex, andcarbon, etc., can be mentioned.

As the inorganic oxide, for example, a single inorganic oxide and acomplex inorganic oxide of 2 kinds or more such as of silica, alumina,zirconia, titania, silica•alumina or silica•zirconia are mentioned.

As the inorganic-organic complex, for example, polyorganosiloxaneobtainable by hydrolysis of metal alkoxide and/or metal alkylalkoxide orthe like are mentioned.

Furthermore, as the carbon, a crystalline carbon or an amorphous carbonis preferably used. As the amorphous carbon, for example, “Bellpearl”(trademark) C-600, C-800, C-2000 (produced by Kanebo, Ltd.), “NICABEADS”(trademark) ICB, PC, MC (produced by Nippon Carbon Co. Ltd.) or the likeare concretely mentioned.

In the conductive particle or fiber [D] of a type coated with aconductive substance, in case where an organic material is used as anucleus or core, as the organic material used as the nucleus or core,thermosetting resins such as an unsaturated polyester resin, a vinylester resin, an epoxy resin, a benzoxazine resin, a phenol resin, anurea-formaldehyde resin, a melamine formaldehyde resin and a polyimideresin, thermoplastic resins such as a polyamide resin, a phenol resin,an amino resin, an acrylic resin, an ethylene polyvinyl acetate resin, apolyester resin, an urea-formaldehyde resin, a melamine formaldehyderesin, an alkyd resin, a polyimide resin, an polyurethane resin, anddivinylbenzene resin are mentioned. And, 2 kinds or more of thematerials mentioned here may be complexed and used. Among them, anacrylic resin or divinylbenzene resin having an excellent heatresistance, and a polyamide resin having an excellent impact resistanceare preferably used.

In the embodiment satisfying the item (2) of the present invention,since the conductive particle or fiber of which thermoplastic resinnucleus or core is coated with a conductive substance [E] is used as anessential component, even when the thermoplastic resin particle or fiber[C] is not added, it is possible to impart a high impact resistance andconductivity to the carbon fiber reinforced composite material. As thethermoplastic resin used as a material of the nucleus or core of theconductive particle or fiber [E] used in the present invention, it ispossible to use the same ones as the above-exemplified various kinds ofthermoplastic resin which are used as the thermoplastic resin by mixingand dissolving in the thermosetting resin. Among them, it is preferableto use a thermoplastic resin of strain energy release rate (G_(1c)) of1500 to 50000 J/m² as the material of nucleus or core. More preferably,it is 3000 to 40000 J/m², still more preferably, 4000 to 30000 J/m².When the strain energy release rate (G_(1c)) is too small, an impactresistance of the carbon fiber reinforced composite material may beinsufficient, and when it is too large, a stiffness of the carbon fiberreinforced composite material may decrease. As such thermoplasticresins, for example, a polyamide, a polyamideimide, a polyethersulfone,a polyetherimide, etc., are preferably used, and a polyamide isespecially preferable. Among polyamides, nylon12, nylon11 or nylon6/12copolymer is preferably used. The evaluation of G_(1c) is, by using aresin plate prepared by molding the thermoplastic resin which is thematerial of nucleus or core of the [E], carried out according to thecompact tension method or the double tension method prescribed in ASTM D5045-96.

In case where a conductive particle of which thermoplastic resin nucleusis coated with a conductive substance is used as the [E], as thethermoplastic resin particle shape, spherical, nonspherical, porous,spicular, whisker-like, or flaky shaped may also be acceptable, butspherical shape is preferable since it is excellent in impregnatingproperty to carbon fibers because it does not lower flow ability of thethermosetting resin. And, since an interlayer delamination, generated bya localized impact when a drop impact (or localized impact) is added tothe carbon fiber reinforced composite material, is more reduced, thedelamination parts, caused by the above-mentioned localized impact,which are starting points of breakage by stress concentration in casewhere a stress is added to the carbon fiber reinforced compositematerial, are not many, and since a contact probability with the carbonfibers in the laminate layer is high to make a conductive paths easy tobe formed, it is preferable since it is possible to obtain a carbonfiber reinforced composite material which realizes a high impactresistance and conductivity.

In case where the conductive fiber of which thermoplastic resin core iscoated with a conductive substance is used as the [E], as a shape of thecore of thermoplastic resin fiber, either of short fiber or long fibercan be used.

In case of the short fiber, as shown in JP-H02-69566A, a method of usingthe short fiber like a particle, or a method of using it by processingit into a mat is possible. In case of the long fiber, as shown inJP-H04-292634A, a method of arranging long fibers in parallel on aprepreg surface, or as shown in WO94016003, a method of arranging inrandom is possible. Furthermore, it is also possible to use it byprocessing it into sheet-like bases such as a woven fabric as shown inJP-H02-32843A, or a non-woven or knitted fabric as shown in WO94016003.And, methods of using as a short fiber chip, a chopped strand, a milledfiber, or using by making the short fiber into a spun yarn, by arrangingin parallel or random, or by processing into a woven or knitted fabric,can also be employed.

At coating the core of thermoplastic resin fiber with the conductivesubstance, a method of coating with the conductive substance after thecore of thermoplastic resin fiber is processed into the above-mentionedshape, or a method of processing into the above-mentioned shape afterthe core of thermoplastic resin fiber is coated with the conductivesubstance, are mentioned.

Either method is preferably employed to the short fiber, long fiber,chopped strand, and milled fiber. In case of the woven fabric, knittedfabric or non-woven fabric, a method of processing them into theabove-mentioned shape after the core of thermoplastic resin fiber iscoated with the conductive substance is preferably used. It is because,in case of the woven fabric, knitted fabric or non-woven fabric, whenthe core of thermoplastic resin particle is coated with the conductivesubstance after processed into such shapes, a coating unevenness isgenerated and a conductivity of the [E] may decrease, and it is notemployed preferably.

In the conductive particle or fiber of which thermoplastic resin nucleusor core is coated with a conductive substance [E], as theabove-mentioned conductive material to coat the nucleus or core, a metalor carbon can be mentioned. And, in such [E], a conductive layer isconstituted with the above-mentioned conductive substance on surface ofthe thermoplastic resin nucleus or core, but such conductive layer maybe a continuous film of metal or carbon, or may be an aggregate offibrous or particulate conductive substance such as a conductive fiber,a carbon black or a metal fine particle. And, an adhesion layer which ismentioned later may be provided between the thermoplastic resin which isthe nucleus or core and the conductive layer.

As the conductive substance constituting the conductive layer in theconductive particle or fiber [D] of the type coated with a conductivesubstance, and in the conductive particle or fiber of whichthermoplastic resin nucleus or core is coated with a conductivesubstance [E], materials which act as an electrically good conductor areacceptable and not limited to those consisting only of a conductor.Preferably, it is a material of which volume resistivity is 10 to 10⁻⁹Ωcm, more preferably 1 to 10⁻⁹ Ωcm, still more preferably 10⁻¹ to 10⁻⁹Ω.When the volume resistivity is too high, in the carbon fiber reinforcedcomposite material, a sufficient conductivity may not be obtained. Forexample, carbon or metal are mentioned, and such a conductive layer maybe a continuous film of a carbon or metal, or an aggregate of fibrous orparticulate conductive substances.

In case where a carbon is used as the conductive substance, carbonblacks such as a channel black, a thermal black, a furnace black, aketjen black, and a hollow carbon fiber, etc., are preferably used.Among them, a hollow carbon fiber is preferably used, and its outerdiameter is preferably 0.1 to 1000 nm, more preferably 1 to 100 nm. Whenthe outer diameter of the hollow carbon fiber is too small or too large,it may be difficult to produce such hollow carbon fibers.

The above-mentioned hollow carbon fiber may have a graphite layer formedon its surface. At that time, a total number of the constitutinggraphite layer is, preferably 1 to 100 layers, more preferably 1 to 10layers, still more preferably, 1 to 4 layers, and especially preferableone has 1 to 2 layers.

In case where a metal is used as the conductive substance, any metal isacceptable, but preferably, its normal electrode potential is −2.0 to2.0V, and more preferably −1.8 to 1.8V. When the normal electrodepotential is too low, it is unstable and may not be preferable in viewof safety, and when it is too high, the processability or productivitymay decrease. Here, the normal electrode potential is expressed bydifference between the electrode potential when a metal is immersed in asolution containing its metal ion and the normal hydrogen electrode(platinum electrode immersed in 1N HCl solution which contact withhydrogen at 1 atm.) potential. For example, Ti: −1.74V, Ni: −0.26V, Cu:0.34V, Ag: 0.80V and Au: 1.52V.

In case where the above-mentioned metal is used, it is preferable to bea metal used by plating. As preferable metals, since a corrosion basedon potential difference with carbon fiber can be prevented, platinum,gold, silver, copper, tin, nickel, titanium, cobalt, zinc, iron,chromium, aluminum, etc., are used and among them, since a highconductivity of volume resistivity 10 to 10⁻⁹ Ωcm and stability areexhibited, platinum, gold, silver, copper, tin, nickel, or titanium areespecially preferably used. Whereas, these metals may be used alone, ormay be used as an alloy of which main components are these metals.

As methods for carrying out metal plating by using the above-mentionedmetal, a wet plating and a dry plating are preferably used. As the wetplating, methods such as electroless plating, displacement plating andelectroplating can be employed, but among them, since it is possible tocarry out plating to a nonconductor, a method by the electroless platingis preferably used. As the dry plating, methods such as vacuum vapordeposition, plasma CVD (chemical vapor deposition), optical chemicalvapor deposition, ion plating and sputtering can be employed, but sinceit is possible to obtain an excellent close contactness at a lowtemperature, a method by the sputtering is preferably employed.

Furthermore, the metal plating may be a coating film of a single metalor a coating film of a plurality of layers of a plurality of metals. Incase where metal plating is carried out, it is preferable that theoutermost surface is formed with a plating film of a layer consisting ofgold, nickel, copper or titanium. By making the outermost surface withthe above-mentioned metal, it is possible to reduce a connectionresistance value or to stabilize the surface. For example, when a goldlayer is formed, a method in which a nickel layer is formed byelectroless nickel plating, and after that, a gold layer is formed by adisplacement gold plating is preferably employed.

Furthermore, it is also preferable to use a metal fine particle as theconductive substance constituting the conductive layer. In this case, asa metal to be used as the metal fine particle, in order to prevent acorrosion due to potential difference with the carbon fiber, platinum,gold, silver, copper, tin, nickel, titanium, cobalt, zinc, iron,chromium, aluminum, or an alloy containing these metals as maincomponents, or tin oxide, indium oxide, indium•tin oxide (ITO), etc.,are preferably used. Among them, because of high conductivity andstability, platinum, gold, silver, copper, tin, nickel, titanium or analloy containing them as main components are especially preferably used.Whereas, at this time, the fine particle means, a particle having anaverage diameter smaller (usually 0.1 times or less is meant) than theaverage diameter of the conductive particle or fiber [D] or of theconductive particle or fiber of which thermoplastic resin nucleus orcore is coated with a conductive substance [E].

As a method of coating the nucleus or core with the above-mentionedmetal fine particle, a mechanochemical bonding technique is preferablyused. The mechanochemical bonding is a method of creating a compositefine particle in which a plural of different material particles aremechanochemically bonded in a molecular level by adding a mechanicalenergy to create a strong nano bond in their interface, and in thepresent invention, the metal fine particle is bonded to the inorganicmaterial or the nucleus or core of organic material, to coat saidnucleus or core with the metal fine particle.

In case where the metal fine particle is coated to the nucleus ofinorganic material or organic material (including thermoplastic resins),a particle diameter of this metal fine particle is preferably 1/1000 to1/10 times of average particle diameter of the nucleus, more preferably1/500 to 1/100 times. A metal fine particle of a too small particlediameter is difficult to be produced in some cases, and on the contrary,when the particle diameter of metal fine particle is too large, acoating unevenness arises in some cases. Furthermore, in case where ametal fine particle is coated to a core of inorganic material or organicmaterial, a particle diameter of this metal fine particle is preferably1/1000 to 1/10 times of average fiber diameter of the core, morepreferably 1/500 to 1/100 times. A metal fine particle of a too smallparticle diameter is difficult to be produced in some cases, and on thecontrary, when the particle diameter of metal fine particle is toolarge, a coating unevenness arises in some cases.

In the conductive particle or fiber [D] and the conductive particle orfiber of which thermoplastic resin nucleus or core is coated with aconductive substance [E] which are types coated with a conductivesubstance, an adhesive layer may not be present between the nucleus orcore and the conductive layer, but it may be present in case where thenucleus or core and the conductive layer are easy to be peeled off. Asmain component of the adhesive layer of this case, a vinyl acetateresin, an acrylic resin, a vinyl acetate-acrylic resin, a vinylacetate-vinyl chloride resin, an ethylene polyvinyl acetate resin, anethylene polyvinyl acetate resin, an ethylene-acrylic resin, apolyamide, a polyvinyl acetal, a polyvinyl alcohol, a polyester, apolyurethane, a urea resin, melamine formaldehyde resin, a phenol resin,a resolcinol resin, an epoxy resin, a polyimide, a natural rubber, achloroprene rubber, a nitrile rubber, an urethane rubber, an SBR, aregenerated rubber, a butyl rubber, an aqueous vinylurethane, anα-olefin, a cyanoacrylate, a modified acrylic resin, an epoxy resin, anepoxy-phenol, a butylal-phenol, a nitrile-phenol, etc., are preferable,and among them, a vinyl acetate resin, an acrylic resin, an vinylacetate-acrylic resin, a vinyl acetate-vinyl chloride resin, an ethylenepolyvinyl acetate resin, an ethylene polyvinyl acetate resin, anethylene-acrylic resin and epoxy resin or the like are mentioned.

In the conductive particle or fiber [D] which is the type coated with aconductive substance and the conductive particle or fiber of whichthermoplastic resin nucleus or core is coated with a conductivesubstance [E], as the conductive particle or fiber which is coated withthe conductive substance, it is good to use those of which volume ratioexpressed by [volume of nucleus or core]/[volume of conductive layer] ispreferably 0.1 to 500, more preferably 1 to 300, still more preferably 5to 100. When such a volume ratio is less than 0.1, not only a weight ofthe obtained carbon fiber reinforced composite material increases, butalso, in the resin compounding, a uniform dispersion may be impossible,and on the contrary, when it exceeds 500, in the obtained carbon fiberreinforced composite material, a sufficient conductivity may not beobtained.

It is preferable that a specific gravity of the conductive particle orfiber used in the present invention (the conductive particle or fiber[D] and the conductive particle or fiber of which thermoplastic resinnucleus or core is coated with a conductive substance [E]) is at most3.2. When the specific gravity of the conductive particle or fiberexceeds 3.2, not only a weight of the obtained carbon fiber reinforcedcomposite material increases, but also, in the resin compounding, auniform dispersion may be impossible. From such a viewpoint, thespecific gravity of the conductive particle or fiber is preferably, 0.8to 2.2. When the specific gravity of the conductive particle or fiber isless than 0.8, in the resin compounding, a uniform dispersion may beimpossible.

As the conductive particle or fiber [D] and the conductive particle orfiber of which thermoplastic resin nucleus or core is coated with aconductive substance [E], in case where a particle is used, its shapemay be spherical, nonspherical, porous, spicular, whisker shaped orflaky, but a spherical one is more excellent in impregnating propertyinto the carbon fiber since it does not impair flow ability of thethermosetting resin. And, since an interlayer delamination, generated bya localized impact when a drop impact (or localized impact) is added tothe carbon fiber reinforced composite material, is more reduced, thedelamination parts, caused by the above-mentioned localized impact,which would be starting points of breakage by stress concentration incase where a stress is added to the carbon fiber reinforced compositematerial, are not many, and since a contact probability with the carbonfibers in the laminate layer is high to make a conductive paths easy tobe formed, it is preferable in view of capability of obtaining a carbonfiber reinforced composite material which realizes a high impactresistance and conductivity.

In case where a fiber is used as the conductive particle or fiber [D]and the conductive particle or fiber of which thermoplastic resinnucleus or core is coated with a conductive substance [E], as its shape,both of short fiber or long fiber can be used. In case of short fiber, amethod of using the short fiber in the same way as particle as shown inJP-H02-69566A or a method of using it by processing it into a mat, ispossible. In case of long fiber, a method of arranging long fibers inparallel on a prepreg surface as shown in JP-H04-292634A, or a method ofarranging randomly as shown in WO94016003 is possible. Furthermore, itcan also be used by processing it into sheet-like bases such as a wovenfabric as shown in JP-H02-32843A, a non-woven fabric, or knitted fabricas shown in WO94016003. And, a short fiber chip, a chopped strand, amilled fiber, or a method in which short fibers are made into a spunyarn and arranged in parallel or random, or processed into a wovenfabric or a knitted fabric can also be employed.

In the conductive fiber [D] and the conductive fiber of which core ofthermoplastic resin fiber is coated with a conductive substance [E]which is a type coated with a conductive substance, a method in which,at coating a material of the core with the conductive substance, afterthe core of conductive fiber is processed into the above-mentionedshape, the conductive substance is coated, or a method in which, aftercoating the core of conductive fiber with the conductive substance, itis processed into the above-mentioned shape, are mentioned. For theshort fiber, long fiber, chopped strand, milled fiber, etc., bothmethods are preferably employed. For the woven fabric, knitted fabric ornon-woven fabric, a method in which, after the conductive substance iscoated to the core of conductive fiber, it is processed into theabove-mentioned shape, is preferably employed. A method in which, afterthe conductive fiber core is processed into the above-mentioned shape,it is coated with the conductive substance is not preferable since acoating unevenness arises and a conductivity of the conductive fiberused as the [D] and [E] may decrease.

In the embodiment the present invention satisfying the item (1) (use ofthe thermoplastic resin particle or fiber together with the conductiveparticle or fiber), a weight ratio expressed by [compounding amount ofthermoplastic resin particle or fiber (parts by weight)]/[compoundingamount of conductive particle or fiber (parts by weight)] is 1 to 1000,preferably 10 to 500 and more preferably 10 to 100. It is because, whenthe weight ratio becomes less than 1, a sufficient impact resistancecannot be obtained in the obtained carbon fiber reinforced compositematerial, and when the weight ratio becomes more than 1000, a sufficientconductivity cannot be obtained in the obtained carbon fiber reinforcedcomposite material.

In the embodiment of the present invention satisfying the item (1) (useof the thermoplastic resin particle or fiber together with theconductive particle or fiber), it is preferable that an average diameterof the conductive particle or fiber [D] (average particle diameter oraverage fiber diameter) is same or more than an average diameter of thethermoplastic resin particle or fiber [C] (average particle diameter oraverage fiber diameter), and the average diameter is at most 150 μm.

In case where the average diameter of the conductive particle or fiber[D] is smaller than the average diameter of the thermoplastic resinparticle or fiber [C], the conductive particle or fiber [D] is buried ininterlayer of the thermoplastic resin particle or fiber [C] which isinsulative, and a conductive path between the carbon fiber in the layerand the conductive particle or fiber [D] is difficult to be formed, anda sufficient improving effect of conductivity may not be obtained.

Furthermore, in the present invention, it is preferable that averagediameters of the thermoplastic resin particle or fiber [C], theconductive particle or fiber [D] and the conductive particle or fiber ofwhich thermoplastic resin nucleus or core is coated with a conductivesubstance [E] are at most 150 μm. When the average diameter exceeds 150μm, since arrangement of the reinforcing fibers is disturbed, or, incase where a particle layer is formed around the prepreg surface, theinterlayer of the obtained composite material becomes thicker thannecessary as mentioned later, physical properties may decrease when itis formed into a composite material. The average diameter is, preferably1 to 150 μm, more preferably 3 to 60 μm, especially preferably 5 to 30μm. When the average diameter is too small, the particle penetratesbetween fibers of the reinforcing fiber and not localizes in theinterlayer portion of the prepreg laminate, and an effect of thepresence of particle is not sufficiently obtained, and an impactresistance may decrease.

Here, method of determination of the average diameters in case of theparticle or in case of the fiber are explained respectively.

As to the average diameter of the particle (average particle diameter),for example, it can be determined as the average value (n=50) of theparticle diameter by photographing the particle at a magnification of1000 times or more by a microscope such as a scanning electronmicroscope, selecting a particle arbitrarily, and taking a diameter ofcircumscribed circle of the particle as the particle diameter. And, whenthe volume ratio expressed by [volume of nucleus]/[volume of conductivelayer] of the conductive particle coated with a conductive substance isdetermined, at first, an average particle diameter of nucleus of theconductive particle is determined by the above-mentioned method, or anaverage diameter of the conductive particle (average particle diameter)is determined by the above-mentioned method. After that, a cross-sectionof the conductive particle coated with a conductive substance isphotographed by a scanning type microscope at a magnification of 10,000times, the thickness of conductive layer is measured (n=10), and itsaverage value is calculated. Such a determination is carried out for theabove-mentioned arbitrarily selected conductive particles (n=50). Theaverage particle diameter of nucleus of the conductive particle and 2times of the average value of thickness of the conductive layer areadded together and taken as the average diameter of conductive particle(average particle diameter), or the average diameter of conductiveparticle (average particle diameter) minus 2 times of the average valueof thickness of the conductive layer is taken to determine the averagediameter of nucleus of the conductive particle (average particlediameter). And, by using the average diameter of nucleus of theconductive particle (average particle diameter) and the average diameterof conductive particle (average particle diameter), it is possible tocalculate a volume ratio expressed by [volume of nucleus]/[volume ofconductive layer].

As to the average diameter of fiber (average fiber diameter), forexample, by a microscope such as a scanning electron microscope, a fibercross-section is photographed at a magnification of 1000 times or more,a fiber cross-section is arbitrarily selected, a diameter ofcircumscribed circle of the fiber cross-section is take as the fiberdiameter, and it is possible to obtain an average value (n=50) of thefiber diameter. And, when the volume ratio expressed by [volume ofcore]/[volume of conductive layer] of the conductive fiber coated withthe conductive substance is determined, first, the average fiberdiameter of core of the conductive fiber is measured by theabove-mentioned means, or the average diameter of the conductive fiber(average fiber diameter) is measured by the above-mentioned means. Afterthat, a cross-section of the conductive fiber coated with the conductivesubstance is photographed by a scanning electron microscope at amagnification of 10,000 times, a thickness of conductive layer ismeasured (n=10), and its average value is calculated. Such a measurementis carried out for the above-mentioned arbitrarily selected conductivefibers (n=50). The average diameter of core of the conductive fiber(average fiber diameter) and 2 times of the average value of thicknessof the conductive layer are added and taken as the average diameter ofthe conductive fiber (average fiber diameter), or the average diameterof the conductive fiber (average fiber diameter) minus 2 times of theaverage value of thickness of the conductive layer is taken to determinethe average diameter of core of the conductive fiber (average fiberdiameter). And, based on the average diameter of core of the conductivefiber (average fiber diameter) and the average diameter of theconductive fiber (average fiber) diameter, it is possible to calculatethe volume ratio expressed by [volume of core]/[volume of conductivelayer].

In the prepreg of the present invention, the carbon fiber weight ratiois preferably 40 to 90%, more preferably 50 to 80%. When the carbonfiber weight ratio is too low, a weight of the obtained compositematerial becomes too heavy, an advantage of the fiber reinforcedcomposite material that is excellent in specific strength and specificmodulus may be impaired, and when the carbon fiber weight ratio is toohigh, a defective impregnation of resin occurs, the obtained compositematerial may have many voids, and its mechanical characteristics maysignificantly decrease.

In the prepreg of the present invention, it is preferable that every oneof the thermoplastic resin particle or fiber [C], conductive particle orfiber [D] and the conductive particle or fiber of which thermoplasticresin nucleus or core is coated with a conductive substance [E]localizes around surface portion of the prepreg. In other words, it ispreferable that a layer abundant in the particles or fibers of theabove-mentioned [C], [D] and [E], that is, a layer in which, when thecross-section is observed, a condition capable of confirming clearlythat the particles or fibers of the above-mentioned [C], [D] and [E]localizes (hereafter, may be referred to as inter-formative layer.), isformed around the surface portion of the prepreg. By this, in case whereprepregs are made into a carbon fiber reinforced composite material bylaying-up and by curing the matrix resin, an interlayer in which theparticles or fibers of the above-mentioned [C], [D] and [E] arelocalized between carbon fiber layers is formed, and by that, sincetoughness of the carbon fiber interlayer increases, and simultaneously,the particles or fibers of the above-mentioned [D] and [E] contained inthe inter-formative layer can form a conductive path in the carbon fiberinterlayer, high level impact resistance and conductivity are exhibitedin the obtained carbon fiber reinforced composite material.

FIG. 1 is an example of a cross-sectional view of a representativeprepreg of the present invention. The present invention is explained inmore detail with reference to FIG. 1.

The prepreg of the present invention shown in FIG. 1 has, between two ofthe carbon fiber layer 1 constituted with the carbon fiber 5 and thethermosetting resin 6, the inter-formative layer 2 containing thethermosetting resin 6, the thermoplastic resin particle 3 and theconductive particle 4. By forming the inter-formative layer 2, sincetoughness of the carbon fiber interlayer increases, and simultaneously,the conductive particle 4 contained in the inter-formative layer 2 canform a conductive path in the carbon fiber interlayer, a high levelimpact resistance and conductivity are exhibited in the obtained carbonfiber reinforced composite material.

From such a viewpoint, it is preferable that the above-mentionedinter-formative layer is present, with respect to the prepreg thickness100%, in the range of 20% thickness from at least one side surface ofthe prepreg, more preferably, in the range of 10% thickness. And, it ispreferable that the above-mentioned inter-formative layer is present, inview of improving convenience at producing the carbon fiber reinforcedcomposite material, on both of front and back sides of the prepreg.

It is preferable that 90 to 100 wt %, preferably 95 to 100 wt % of theparticles or fibers of the above-mentioned [C], [D] and [E], withrespect to the respective total amounts, localize in the above-mentionedinter-formative layer.

The thickness of the above-mentioned inter-formative layer with respectto the prepreg and the containing ratio of the particles or fibers ofthe above-mentioned [C], [D] and [E] contained in said inter-formativelayer can be evaluated, for example, by the following method.

As to the thickness of the inter-formative layer with respect to theprepreg, a plural of laid-up prepregs are contacted closely by holdingbetween 2 smooth surface polytetrafluoroethylene resin plates, andgelled and cured by gradually raising temperature to curing temperaturein 7 days to prepare a platy cured prepreg product. By using this curedprepreg, a magnified photograph of the cross-section is taken. By usingthis cross-section photograph, a thickness of the inter-formative layerwith respect to the prepreg is measured. In concrete, on a photographsuch as shown in FIG. 1, it is measured at arbitrarily selected at least10 positions of the inter-formative layer 2 between the carbon fiberlayers 1, and their average is taken as a thickness of theinter-formative layer.

As to the containing ratio of particles or fibers of the above-mentioned[C], [D] and [E] contained in the inter-formative layer, a single layerprepreg is closely contacted by holding between 2 smooth surfacepolytetrafluoroethylene resin plates, gelled and cured by graduallyraising temperature to curing temperature in 7 days to prepare a platycured prepreg product. On both sides of this prepreg, 2 lines which areparallel to the surface of cured product of the prepreg are drawn atpositions of 20% depth, with respect to the thickness, from the surfaceof the cured product. Next, a total area of the above-mentioned particleor fiber present between the prepreg surface and the above-mentionedlines, and a total area of the particle or fiber present throughout thethickness of prepreg are determined, and calculate the containing ratioof the particle or fiber present in 20% depth range from the prepregsurface, with respect to the prepreg thickness 100%. Here, the totalarea of the above-mentioned particle or fiber is determined by clippingthe particle or fiber portion from the cross-section photograph andweighing its weight. In case where a distinction of particles dispersedin the resin after taking a photograph is difficult, a means of dyeingthe particle can also be employed.

Furthermore, in the present invention, it is preferable that a totalamount of the thermoplastic resin particle or fiber [C], the conductiveparticle or fiber [D] and the conductive particle or fiber of whichthermoplastic resin nucleus or core is coated with a conductivesubstance [E] is, with respect to the prepreg, in the range of 20 wt %or less. When the total amount of the particles or fibers of theabove-mentioned [C], [D] and [E] exceeds, with respect to the prepreg,20 wt %, not only it becomes difficult to mix with the base resin, butalso tack and draping properties of the prepreg may decrease. That is,in order to impart impact resistance while maintaining characteristicsof the base resin, it is preferable that the total amount of theparticles or fibers of the above-mentioned [C], [D] and [E] is, withrespect to the prepreg, 20 wt % or less, more preferably 15 wt % orless. In order to make handling of the prepreg still more excellent, itis more preferable to be 10 wt % or less. It is preferable that thetotal amount of the particles or fibers of the above-mentioned [C], [D]and [E] is, in order to achieve a high impact resistance andconductivity, with respect to the prepreg, 1 wt % or more, morepreferably 2 wt % or more.

In the present invention, among the conductive particle or fiber [D] andthe conductive particle or fiber of which thermoplastic resin nucleus orcore is coated with a conductive substance [E], there are some of whichadhesion with the thermosetting resin [B] are low, but when thosesubjected to a surface treatment are used, it is possible to realize astrong adhesion with the thermosetting resin, and a further improvementof impact resistance becomes possible. From such a viewpoint, it ispreferable to use those subjected to at least one kind of treatmentselected from the group consisting of a coupling treatment, an oxidationtreatment, an ozonation, a plasma treatment, a corona treatment, and ablast treatment. Among them, those subjected to a surface treatment of acoupling treatment, an oxidation treatment or a plasma treatment whichis capable of forming a chemical bond or hydrogen bond with thethermosetting resin is preferably used since a strong adhesion with thethermosetting resin can be realized.

Furthermore, at the above-mentioned surface treatment, in order toshorten the surface treatment time or to assist the dispersion of theconductive particle or fiber [D] and the conductive particle or fiber ofwhich thermoplastic resin nucleus or core is coated with a conductivesubstance [E], it is possible to carry out the surface treatment whileapplying heat and ultrasonic wave. It is preferable that the heatingtemperature is at most 200° C., preferably 30 to 120° C. That is, whenthe temperature is too high, a bad smell may be generated to worsen theenvironment or operation cost may increase.

As a coupling agent used for the coupling treatment, a silane-based, atitanium-based or an aluminum-based one is used, and these couplingagent may be used alone or in combination. When a coupling agent is notappropriate, since adhesion with the treated particle or fiber and thethermosetting resin becomes insufficient, impact resistance maydecrease. In order to avoid such a problem, it is preferable to use acoupling agent having a strong affinity to, or capable of chemicalbonding to realize a strong adhesion with a thermosetting resin to beused. In order to increase the affinity to the thermosetting resin, itis preferable to select a coupling agent having a substituted group ofwhich molecular structure or polarity is similar to the molecularstructure or polarity of a thermosetting resin to be used.

In order to surely increase adhesion further, it is preferable to use acoupling agent capable of forming a chemical bond with the thermosettingresin which is the matrix resin. In case where a resin capable ofradical polymerization such as an unsaturated polyester resin, a diallylphthalate resin or a maleimide resin is the matrix resin, a couplingagent having a substituted group with a double bond such as vinyl group,allyl group, acryloyl group, methacryloyl group, cyclohexenyl group, incase where an epoxy resin is the matrix resin, a coupling agent havingepoxy group, phenolic hydroxyl group, carboxyl group, mercapto group,amino group or a monosubstituted amino group, in case where a phenolresin is the matrix resin, a coupling agent having epoxy group orphenolic hydroxyl group, in case where a polyurethane resin is thematrix resin, a coupling agent having hydroxyl group, amino group or amonosubstituted amino group, in case where a melamine formaldehyde resinor a urea-formaldehyde resin is the matrix resin, a coupling agenthaving amide group, ureido group, amino group or a monosubstituted aminogroup, in case where a maleimide resin is the matrix resin, other than acoupling agent having a double bond, a coupling agent having amino groupor a monosubstituted amino group, in case where a cyanate resin is thematrix resin, a coupling agent having carboxyl group, epoxy group,hydroxyl group, amino group or a monosubstituted amino group, canpreferably be used.

As a coupling treatment, silane coupling treatment is preferable sincecoupling agents having various functional groups are easily available.As concrete examples of the silane coupling agent, as aminosilanes,3-aminopropyl trimethoxysilane, 3-aminopropyl triethoxysilane,3-(2-aminoethyl)aminopropyl trimethoxysilane, 3-(phenylamino)propyltrimethoxysilane, 3-(2-aminoethyl)amino-3-(2-aminoethyl)aminopropylmethyl dimethoxysilane, etc., asepoxysilanes, 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyl dimethoxysilane,2-(3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, etc., as vinylsilanes, vinyltrichlorosilane,vinyltrimethoxysilane, vinyltriethoxysilane,vinyltris(2-methoxyethoxy)silane, vinyltriacetoxysilane, etc., can bementioned. In particular, a silane coupling agent having an epoxy group,amino group or a monosubstituted amino grouping in molecule isespecially preferably used since it is applicable to a wide range ofresin and its reactivity is also high.

In the present invention, in case where the conductive particle or fiber[D] and the conductive particle or fiber of which thermoplastic resinnucleus or core is coated with a conductive substance [E] (hereafter,may be referred to as substance to be treated) are subjected to acoupling treatment, it is preferable to compound a coupling agent, withrespect to these particle or fiber 100 parts by weight, preferably 0.01to 30 parts by weight, more preferably 0.1 to 10 parts by weight. Whenthe compounding amount of the coupling agent is too small, an adhesionwith the thermosetting resin may not be sufficiently exhibited, and onthe contrary, when it is too large, mechanical properties of curedproduct may decrease.

In the present invention, a coupling treatment may be carried out byattaching a coupling agent to the substance to be treated and heattreating directly, or the coupling agent and the substance to be treatedare added to the thermosetting resin beforehand, and the couplingtreatment may also be carried out by a heat treatment at curing theprepreg.

As the oxidation treatment, it is not especially limited as far as thesurface of the substance to be treated can be oxidized, but it ispossible to employ a chemical liquid oxidation treatment and anelectrolytic oxidation treatment. Among them, a chemical liquidoxidation treatment is preferably used.

The chemical liquid oxidation treatment is a method of oxidationtreatment in an acidic aqueous solution. As the acidic aqueous solution,for example, an aqueous solution containing sulfuric acid, fumingsulfuric acid, nitric acid, fuming nitric acid, hydrochloric acid,phosphoric acid, carbonic acid, boric acid, oxalic acid, fluoric acid,formic acid, butyric acid, acetic acid, boric acid-sulfuric acid,chlorosulfuric acid, chloroacetic acid, sulfosalicylic acid,sulfoacetate, maleic acid, chromic anhydride, hypochlorous acid, acrylicacid, sulfonic acid, fluorosulfonic acid, trifluoromethane sulfuricacid, trifluoromethane sulfonic acid, ammonium sulfate, ammoniumformate, ammonium dihydrogen phosphate, ammonium oxalate, ammoniumhydrogen sulfate, etc., may be used alone or in combination. Bysubjecting to the oxidation treatment, a functional group such ashydroxyl group or carboxyl group is chemically generated on thesubstance to be treated, and a strong adhesion is realized by lettingthe functional group make a chemical bond and/or hydrogen bond with thematrix resin. Among them, sulfuric acid, nitric acid or mixed acidthereof which shows strong acidity are preferably used.

As to a concentration of the acidic aqueous solution, it is preferably0.01 wt % or more, more preferably 10 wt % or more and still morepreferably 50 wt % or more. As the concentration becomes higher, thetreatment time becomes shorter or there is more effect of loosening anaggregation of the substance to be treated. When an oxidant such asozone, hydrogen peroxide, lead dioxide is added to the acidic aqueoussolution, it is preferable since the oxidizing power increases.

As the surface treatment by ozone, in general, a method in which thesubstance to be treated is heat treated by introducing ozone into achamber having a heater is preferably used. In this case, surface of theabove-mentioned particle or fiber is modified to an activated surface,and surface wettability with the matrix resin is greatly improved, toenable to realize a strong adhesion. Furthermore, a method in which thesubstance to be treated is subjected to a photo oxidation treatment byan ultraviolet light irradiation under an ozone atmosphere is preferablyemployed.

As the surface treatment by plasma, a method of subjecting to a plasmatreatment under reduced pressure by introducing a reactive gas into achamber is preferably employed. As the reactive gas, helium, neon,argon, nitrogen, ammonia, oxygen, nitrous oxide, nitrogen monooxide,nitrogen dioxide, carbon monooxide, carbon dioxide, cyanogen bromide,hydrogen cyanide, hydrogen, steam, air, sulfur dioxide gas, hydrogensulfide, etc., may be used alone or in combination. By carrying out aplasma treatment to the substance to be treated, it is modified to anactivated surface, and surface wettability with the matrix resin isgreatly improved, to enable to realize a strong adhesion.

As discharge frequencies (alternating current) of the plasma, a highfrequency wave, a low frequency wave or a microwave can be used, and adirect current can also be used. As treating apparatuses, there are aninternal electrode system in which an electrode is installed inside avacuum apparatus and an external electrode system in which an electrodeis installed outside the vacuum apparatus, but in the present invention,both systems can be used. As to the electrode shape, a platy, rod-like,cylindrical can be used in combination depending on its purpose, butwhen, as a discharge electrode, a metal rod of its surface is coatedwith a glass, and as an earth electrode, a metal, for example, stainlesssteel plate or drum are used in an interval between electrodes of,preferably 0.5 to 30 cm, more preferably 2 to 10 cm, it is preferablesince there is no discharge unevenness, to enable a uniform treatment.It is preferable that the electrode is cooled with water or the like, ifnecessary.

As the surface treatments by the corona treatment, for example, methodsdisclosed in JP-S48-5043B, JP-S47-51905B, JP-S47-28067A, JP-S49-83767A,JP-S51-41770A, JP-S51-131576A, etc., can be employed. By carrying outthe corona treatment to the substance to be treated, it is modified intoan activated surface, and surface wettability with the matrix resin isgreatly improved, to enable to realize a strong adhesion.

As surface treatments by the blast treatment, there are a wet method anda dry method, and they are carried out by blasting a fine particleprojectile material contained in water or compressed air flow to surfaceof the conductive particle or fiber [D] and the conductive particle orfiber of which thermoplastic resin nucleus or core is coated with aconductive substance [E] and they are treating methods preferablyemployed to the conductive fibers [D] and [E]. By this way, the surfacearea is enlarged by forming fine unevenness on its surface, and it ispossible to increase adhesion power between the matrix resin and thesubstance to be treated. As kinds of the projectile material, forexample, glass beads, silicic anhydride, alumina, diamond, red ironoxide, etc., are mentioned. And, as a particle diameter of theprojectile material, approximately 100 to 5000 μm is used in many cases.Generally saying, by selecting kind of the projectile material, particlediameter and ejecting pressure of the projectile material according toits purpose, it is possible to carry out the surface treatment into themost appropriate surface roughness.

The prepreg of the present invention can be produced by applyingpublicly known methods such as disclosed in JP-H01-26651A,JP-S63-170427A or JP-S63-170428A.

In concrete, the following 3 methods can be exemplified.

First method is a method in which, by putting and pressing a resin film,of the thermosetting resin [B] coated on a release paper or the like, toboth sides or one side of the carbon fiber [A] paralleled in sheet like,to impregnate with the thermosetting resin [B], to prepare a primaryimpregnate prepreg, and a separate resin film containing at least one ofthe following (1) and (2) in the thermosetting resin [B] is sticked onits both sides or one side.

(1) the thermoplastic resin particle or fiber [C] and the conductiveparticle or fiber [D]

(2) the conductive particle or fiber of which thermoplastic resinnucleus or core is coated with a conductive substance [E]

Here, instead of putting the separate resin film containing at least anyone of the items (1) and (2) in the thermosetting resin [B], it is alsopossible to scatter or put at least any one of the items (1) and (2)only on the above-mentioned primary impregnate prepreg.

Second method is a method in which, to the primary impregnate prepregprepared by the first method, a separate resin film of the thermosettingresin [B] coated on a release paper or the like of which surface atleast any one of the above-mentioned (1), (2) is scattered or sticked,is sticked to both sides or one side of the above-mentioned primaryimpregnate prepreg.

Third method is a method in which a resin film, in which thethermosetting resin [B] containing at least any one of theabove-mentioned (1), (2) is coated on a release paper or the like, isput and pressed to both sides or one side of the carbon fiber [A]paralleled in sheet like, to impregnate with the thermosetting resin [B]containing at least any one of the above-mentioned (1), (2), to preparea prepreg.

The carbon fiber reinforced composite material of the present inventioncan be produced by laying-up the above-mentioned prepreg of the presentinvention, and by heat•pressing to cure the heat curable resin [B].Here, as a method for imparting heat•pressing, a press forming, anautoclave molding, a bag molding method, a wrapping tape method and aninternal pressure molding method, etc., are employed, and especially theautoclave molding is preferably employed.

The carbon fiber reinforced composite material of the present inventionis, since it is excellent in strength, stiffness, impact resistance andconductivity, etc., widely used in aerospace application and in generalindustrial application, etc. In more concrete, in the aerospaceapplication, it is preferably used for an aircraft primary structuralmember application such as main wing, tail wing and floor beam, for anaircraft secondary structural member application such as flap, aileron,cowl, fairing and interior material, and for rocket motor case andartificial satellite structural material application, etc. Among suchaerospace applications, especially aircraft primary structural materialapplications in which impact resistance and lightning protection arenecessary, especially for fuselage skin, main wing skin and tail wingskin, the carbon fiber reinforced composite material by the presentinvention is especially preferably used. And, in general industrialapplications, it is preferably used for structural material of mobilessuch as cars, ships and railway vehicles, and for a driveshaft, a leafspring, a windmill blade, a pressure vessel, a flywheel, a roller forpaper making, a roofing material, a cable, a reinforcing bar, anapplication for computer such as an IC tray or kyotai (housing) ofnotebook computer and for a civil engineering/building application suchas a repairing/reinforcing material, etc. Among them, for an automotiveouter panel, an outer panel of ship, an outer panel of railway vehicle,a windmill blade and an IC tray or kyotai (housing) of notebookcomputer, the carbon fiber reinforced composite material by the presentinvention is especially preferably used.

EXAMPLES

Hereafter, the present invention is explained in more detail withreference to the examples. In order to obtain the prepreg of eachexample, the following materials were used.

<Carbon Fiber>

-   -   “Torayca (trademark)” T800S-24K-10E (carbon fiber, number of        fiber 24,000 fibers, tensile strength 5.9 GPa, tensile modulus        290 GPa, tensile strain 2.0%, produced by Toray Industries,        Inc.)    -   “Torayca (trademark)” T700S-24K-50C (carbon fiber, number of        fiber 24,000 fibers, tensile strength 4.9 GPa, tensile modulus        230 GPa, tensile strain 2.1%, produced by Toray Industries,        Inc.)

<Thermosetting Resin>

-   -   Bisphenol A type epoxy resin, “Epikote (trademark)” 825        (produced by Japan Epoxy Resins Co., Ltd.)    -   Tetraglycidyldiaminodiphenylmethane, ELM434 (produced by        Sumitomo Chemical Co., Ltd.)    -   Polyethersulfone having hydroxyl group on its ends “Sumikaexcel        (trademark)” PES5003P (produced by Sumitomo Chemical Co., Ltd.)    -   4,4′-Diaminodiphenyl sulfone (produced by Mitsui Fine Chemical        Inc.)

<Thermoplastic Resin Particle>

-   -   Nylon12 particle SP-10 (produced by Toray Industries, Inc.,        shape: true sphere)    -   Epoxy modified nylon particle A obtained by the following        production method

A transparent polyamide (“Grilamid (trademark)”—TR55, produced by EMSERWERKE AG) 90 parts by weight, epoxy resin (product name “Epikote(trademark)” 828, produced by Yuka-Shell Epoxy Co., Ltd.) 7.5 parts byweight and a hardener (product name “Tohmide (trademark)” #296, producedby Fuji Kasei Kogyo Co., Ltd.) 2.5 parts by weight were added to a mixedsolvent of chloroform 300 parts by weight and methanol 100 parts byweight, to obtain a uniform solution. Next, the obtained uniformsolution was misted by a spray gun for painting, well stirred andsprayed to liquid surface of n-hexane of 3000 parts by weight, toprecipitate the solute. The precipitated solid was filtered, and afterfully washed by n-hexane, vacuum dried at a temperature of 100° C. for24 hours, to obtain a true spherical epoxy modified nylon particle A.

After the epoxy modified nylon particle A was press-molded into a resinplate, in accordance with ASTM D 5045-96, when G_(1c) value wasdetermined by compact tension method, it was found to be 4420 J/m².

<Thermoplastic Resin Fiber>

-   -   TR-55 short fiber obtained by the following production method

A transparent polyamide (product name “Grilamid (trademark)”—TR55,produced by EMSER WERKE AG) fiber extruded from a spinneret equippedwith one orifice was cut and a TR-55 short fiber (fiber length 1 mm) ofwhich cross-sectional shape is perfect circle was obtained.

After the TR-55 was press-molded into a resin plate, when G_(1c) valueby compact tension method was determined in accordance with ASTM D5045-96, it was found to be 4540 J/m².

<Conductive Particle>

-   -   “Micropearl (trademark)” AU215 (produced by Sekisui Chemical        Co., Ltd., shape: true sphere, specific gravity: 1.8 g/cm³,        thickness of conductive layer: 110 nm, [volume of        nucleus]/[volume of conductive layer]: 22.8) which is a particle        in which a divinylbenzene polymer particle is plated by nickel        and further plated by gold thereon    -   “Micropearl (trademark)” AU225 (produced by Sekisui Chemical        Co., Ltd., shape: true sphere, specific gravity: 2.4 g/cm³,        thickness of conductive layer: 200 nm, [volume of        nucleus]/[volume of conductive layer]: 20.2) which is a particle        in which a divinylbenzene polymer particle is plated by nickel        and further plated by gold thereon    -   Glassy carbon particle “Bellpearl (trademark)” C-2000 (produced        by Air Water Inc., shape: true sphere, specific gravity: 1.5        g/cm³)    -   Conductive particle B (shape: true sphere, specific gravity: 1.3        g/cm³) obtained by the following production method

Ferrous acetate (produced by Sigma-Aldrich Co.) 0.01 g and cobaltacetate tetrahydrate (produced by Nacalai Tesque, Inc.) 0.21 g wereadded to ethanol (produced by Nacalai Tesque, Inc.) 40 ml, and suspendedfor 10 minutes by an ultrasonic washer. To this suspension, crystallinetitanosilicate powder (produced by N.E. Chemcat Corp. “Titanosilicate(trademark)”) (TS-1) 2.0 g was added, and treated by the ultrasonicwasher for 10 minutes, and by removing the methanol under a constanttemperature of 60° C., a solid catalyst in which the above-mentionedmetal acetate is supported by TS-1 crystal surface was obtained.

The solid catalyst 1.0 g prepared in the above-mentioned was put on aquartz boat in center portion of a quartz tube of inner diameter 32 mm,and argon gas fed at 600 cc/min. The quartz tube was placed in anelectric furnace and its center temperature was heated to a temperatureof 800° C. (heating time 30 minutes). When the temperature arrived at800° C., after a high purity acetylene gas (produced by Koatsu Gas KogyoCo., Ltd.) was fed at 5 cc/min for 30 minutes, the feed of acetylene gaswas stopped and the temperature was cooled down to room temperature, anda composition containing a hollow carbon nanofiber was taken out. Thecomposition containing the obtained hollow carbon nanofiber 0.4 g wasput in an electric furnace and heated to 400° C. (heating time 40minutes) under an atmospheric environment. After keeping at atemperature of 400° C. for 60 minutes, it was cooled down to roomtemperature. Furthermore, after this composition containing the hollowcarbon nanofiber was thrown into 2.5 mol/L aqueous solution of sodiumhydroxide 200 ml, the solution was stirred for 5 hours while keeping ata temperature of 80° C. After that, it was suction-filtered by amembrane filter of 10 μm diameter, to carry out a solid/liquidseparation. After washing the obtained solid by distilled water 1 L, itwas thrown into 5.1 mol/L concentration sulfuric acid 50 ml, and stirredfor 2 hours while keeping at a temperature of 80° C. After that, thesolid substance was separated by using a filter paper (produced by ToyoRoshi Kaisha, Ltd.), Filter Paper No. 2 of 125 mm. After the solidsubstance on the filter paper was washed by distilled water 500 ml, itwas dried at a temperature of 60° C., to obtain a hollow carbonnanofiber at a recovery yield of 90%.

In ethanol 100 ml, the hollow carbon fiber obtained in theabove-mentioned 5 g and the epoxy modified nylon particle A obtained inthe item of the above-mentioned thermoplastic resin particle 23 g wereadded, and stirred for 1 hour to obtain a suspended liquid. The obtainedsuspended liquid was concentrated under reduced pressure. Subsequently,by curing by heating to a temperature of 200° C. under argon atmosphere,a conductive particle B 25 g was obtained. When a cross-section of thisconductive particle B was observed by a scanning electron microscope, itwas fount that a conductive layer was formed in a thickness of 300 nm.[Volume of nucleus]/[volume of conductive layer] was 7.0.

-   -   Conductive particle C obtained by the following production        method

By using sputtering apparatus CFS-4ES-231 (produced by ShibauraMechatronics Corp.), the epoxy modified nylon particle A 10 g was put ona base plate and a sputtering was carried out in a condition in whichtarget was copper, gas component was argon, gas pressure was 2.0×10⁻¹Pa, base plate temperature was 80° C. and electric power was 500W, toprepare a conductive particle C of which thickness of conductive layerwas 110 nm. It was found that the shape of conductive particle was truesphere, the specific gravity was 1.4 g/cm³ and the [volume ofnucleus]/[volume of conductive layer] was 18.6.

-   -   Conductive particle D obtained by the following production        method

By using sputtering apparatus CFS-4ES-231 (produced by ShibauraMechatronics Corp.), the epoxy modified nylon particle A 10 g was put ona base plate and a sputtering was carried out in a condition in whichtarget was titanium, gas component was argon, gas pressure was 3.0×10⁻¹Pa, base plate temperature was 80° C. and electric power was 500 W, toprepare a conductive particle D of which thickness of conductive layerwas 130 nm. It was found that the shape of conductive particle was truesphere, the specific gravity was 1.3 g/cm³ and the [volume ofnucleus]/[volume of conductive layer] was 15.7.

-   -   Conductive particle E obtained by the following production        method

The epoxy modified nylon particle A 100 g was added to 1000 ml ofelectroless copper plating liquid MK-430 (produced by Muromachi ChemicalInc.), and subsequently a plating treatment was carried out at 50° C.for 45 minutes, to prepare a conductive particle E. It was found thatthe shape of conductive particle E was true sphere, the specific gravitywas 1.4 g/cm³, the thickness of conductive layer was 120 nm, and the[volume of nucleus]/[volume of conductive layer] was 17.0.

Conductive particle F obtained by the following production method

The epoxy modified nylon particle A 100 g was added to 1000 ml ofelectroless nickel plating liquid NLT-PLA (produced by Nikko MetalPlating Co., Ltd.), and subsequently a plating treatment was carried outat 50° C. for 60 minutes, to prepare a conductive particle F. It wasfound that the shape of conductive plate F was true sphere, the specificgravity was 1.4 g/cm³, the thickness of conductive layer was 180 nm, andthe [volume of nucleus]/[volume of conductive layer] was 11.2.

-   -   Conductive particle G obtained by the following production        method

Transparent polyamide (product name “Grilamid (trademark)”—TR55,produced by EMSER WERKE AG) 60 parts by weight, epoxy resin (productname “Epikote (trademark)” 828, produced by Japan Epoxy Resins Co.,Ltd.) 30 parts by weight and a hardener (product name “Tohmide(trademark)” #296, produced by Fuji Kasei Kogyo Co., Ltd.) 10 parts byweight were added to a mixed solvent of chloroform 300 parts by weightand methanol 100 parts by weight, to obtain a uniform solution. Next,the obtained uniform solution was misted by a spray gun for painting,well stirred and sprayed to liquid surface of n-hexane of 3000 parts byweight, to precipitate the solute. The precipitated solid was separatedby filtration, and after fully washed by n-hexane, vacuum dried at atemperature of 100° C. for 24 hours, to obtain a true spherical epoxymodified nylon particle H.

The epoxy modified nylon particle H 100 g was added to 1000 mlelectroless copper plating liquid MK-430 (produced by Muromachi ChemicalInc.), subsequently a plating treatment was carried out at 50° C. for 45minutes, to prepare conductive particle G. It was found that the shapeof conductive plate G was true sphere, the specific gravity was 2.2g/cm³, the thickness of conductive layer was 320 nm, and the [volume ofnucleus]/[volume of conductive layer] was 6.2.

After the epoxy modified nylon particle H was press-molded into a resinplate, when G_(1c) value by compact tension method was determined inaccordance with ASTM D 5045-96, it was found to be 1210 J/m².

-   -   Surface Treated Article I of “Micropearl (Trademark)” AU215        Obtained by the Following Production Method

3-(phenylamino) propyltrimethoxysilane 2 parts by weight was sprayed,while being stirred by a mixer, to “Micropearl (trademark)” AU215 100parts by weight, subsequently heat treated at 100° C. for 12 hours, toobtain a surface treated article I of “Micropearl (trademark)” AU215.

-   -   Surface treated article J of “Bellpearl(trademark)” C-2000        obtained by the following production method

“Bellpearl (trademark)” C-2000 100 g was added to 98 wt % sulfuric acidsolution 150 ml and 60 wt % nitric acid solution 50 ml, subsequentlystirred at 120° C. for 20 minutes and after separated by a filter, fullywashed with water, to obtain a surface treated article J of “Bellpearl(trademark)” C-2000.

<Conductive Fiber>

-   -   “Torayca (trademark)” milled fiber MLD-30 (produced by Toray        Industries, Inc., cross-sectional shape: perfect circle,        specific gravity: 1.8 g/cm³, fiber length 30 μm)    -   “Torayca (trademark)” chopped fiber T008-3 (produced by Toray        Industries, Inc., cross-sectional shape: perfect circle,        specific gravity: 1.8 g/cm³, fiber length 3 mm)    -   Conductive fiber A obtained by the following production method

TR-55 short fiber (fiber length 1 mm) 100 g was added to electrolesscopper plating liquid MK-430 (produced by Muromachi Chemical Inc.) 1000ml, subsequently a plating treatment was carried out at 50° C. for 45minutes, to obtain a conductive fiber A. It was found thatcross-sectional shape of the conductive fiber A was perfect circle,specific gravity was 1.6 g/cm³, the thickness of conductive layer was100 nm, the [volume of core]/[volume of conductive layer] was 13.3.

Whereas, determination of average diameter of the thermoplastic resinparticle or fiber [C], the conductive particle or fiber [D] and theconductive particle or fiber of which thermoplastic resin nucleus orcore is coated with a conductive substance [E], containing ratio of theparticles or fibers of the above-mentioned [C], [D] and [E] present inthe depth range of 20% of prepreg thickness, compressive strength afterimpact and conductivity of fiber reinforced composite material werecarried out in the following conditions. Except where it is explicitlystated otherwise, the determinations were carried out in an environmentof a temperature of 23° C. and a relative humidity of 50%.

(1) Determinations of Average Diameters of Particles [C], [D] and [E]and Volume Ratio Expressed by [Volume of Nucleus]/[Volume of ConductiveLayer] of Conductive Particle Coated with Conductive Substance

As to the average diameter of the particle, for example, it wasdetermined as the average value (n=50) of particle diameters byphotographing particles at a magnification of 1000 times or more by amicroscope such as scanning electron microscope, selecting a particlearbitrarily, and taking diameter of circumscribed circle of the particleas the particle diameter. And, when a volume ratio expressed by [volumeof nucleus]/[volume of conductive layer] of conductive particle coatedwith a conductive substance is determined, at first, an average particlediameter of nucleus of the conductive particle (average particlediameter) is measured by the above-mentioned method, and after that, across-section of the conductive particle coated with a conductivesubstance is photographed by a scanning type microscope at amagnification of 10,000 times, the thickness of conductive layer wasmeasured (n=10), and its average value was calculated. Such adetermination was carried out for the above-mentioned arbitrarilyselected conductive particles (n=50). The average particle diameter ofnucleus of the conductive particle and 2 times of the average value ofthickness of the conductive layer were added together and taken as theaverage diameter of conductive particle (average particle diameter).And, based on the average diameter of nucleus of the conductive particle(average particle diameter) and the average diameter of conductiveparticle (average particle diameter), a volume ratio expressed by[volume of nucleus]/[volume of conductive layer] was calculated.Whereas, in case where a particle was nonspherical, supposingcircumscribed sphere of the nucleus, a calculated value calculated bysupposing a sphere coated on the circumscribed sphere with theconductive layer measured by the above-mentioned method was taken as avolume ratio.

Determination results of average particle diameter of each particle ofthe thermoplastic resin particle and the conductive particle were asfollows.

<Thermoplastic Resin Particle>

Nylon 12 particle SP-10 (produced by Toray Industries, Inc.) 10.2 μmEpoxy modified nylon particle A 12.5 μm

<Conductive Particle>

“Micropearl” AU215 15.5 μm “Micropearl” AU225 25.0 μm “Bellpearl” C-200015.3 μm Conductive particle B 13.8 μm Conductive particle C 12.7 μmConductive particle D 12.9 μm Conductive particle E 12.7 μm Conductiveparticle F 13.0 μm Conductive particle G 13.1 μm Surface treated articleI of “Micropearl” AU215 15.5 μm Surface treated article J of“Bellpearl”C-2000 15.3 μm

(2) Determination of Average Fiber Diameter the Fiber of [C], [D] and[E] and the Volume Ratio Expressed by [Volume of Core]/[Volume ofConductive Layer] of the Conductive Fiber Coated with the ConductiveSubstance

As to the average diameter of the fiber (average fiber diameter), forexample, it was determined as the average value (n=50) of fiberdiameters by photographing fibers at a magnification of 1000 times ormore by a microscope such as scanning electron microscope, selecting afiber cross-section arbitrarily, and taking diameter of circumscribedcircle of the fiber as the fiber diameter. And, when a volume ratioexpressed by the [volume of nucleus]/[volume of conductive layer] ofconductive fiber coated with a conductive substance is determined, atfirst, an average fiber diameter of nucleus of the conductive fiber(average fiber diameter) is measured by the above-mentioned method. Andafter that, a cross-section of the conductive fiber coated with aconductive substance is photographed by a scanning type microscope at amagnification of 10,000 times, the thickness of conductive layer wasmeasured (n=10), and its average value was calculated. Such adetermination was carried out for the above-mentioned arbitrarilyselected conductive fibers (n=50). The average fiber diameter of nucleusof the conductive fiber and 2 times of the average value of thickness ofthe conductive layer were added together and taken as the averagediameter of conductive fiber (average fiber diameter). And, by using theaverage diameter of nucleus of the conductive fiber and the averagediameter of conductive fiber, a volume ratio expressed by the [volume ofnucleus]/[volume of conductive layer] was calculated. Whereas,determination result of average fiber diameter of each fiber of thethermoplastic resin fiber and of the conductive fiber was as follows.

<Thermoplastic Resin Fiber>

TR-55 short fiber 5.4 μm

<Conductive Fiber>

“Torayca” milled fiber MLD-30 7.2 μm “Torayca” chopped fiber T008-3 6.9μm Conductive fiber A 5.6 μm

(3) Containing Ratio of the Particle or Fiber of [C], [D] and [E]Present in Depth Range of 20% of Prepreg Thickness

A prepreg was held and closely contacted between 2 smooth surfacepolytetrafluoroethylene resin plates, and gelled and cured by graduallyraising temperature up to 150° C. in 7 days to prepare a platy curedprepreg product. After the curing, it was cut in a directionperpendicular to the closely contacted surface, and after thecross-section was polished, it was magnified 200 times or more by anoptical microscope and photographed such that the upper and lowersurfaces of the prepreg were into view. By the same procedure, distancebetween the polytetrafluoroethylene resin plate were measured at 5positions in horizontal direction of the cross-section photograph andtheir average value (n=10) was taken as the thickness of prepreg.

On both sides of the photograph of this cured product of the prepreg, 2lines which are parallel to the surface of the prepreg are drawn atpositions of 20% depth from the surface of the cured product of prepreg.Next, a total area of the above-mentioned particle or fiber presentbetween the prepreg surface and the above-mentioned line, and a totalarea of the particle or fiber present throughout the thickness of theprepreg are determined, and calculate the containing ratio of theparticle or fiber present in 20% depth range from the prepreg surface,with respect to the prepreg thickness 100%. Here, the total area of theabove-mentioned particle or fiber is determined by clipping the particleor fiber portion from the cross-section photograph and weighing itsweight. In case where a distinction of particles dispersed in the resinafter taking a photograph was difficult, the particle was photographedafter dyeing, appropriately.

(4) Determination of Volume Resistivity of Conductive Particle or Fiber

By using MCP-PD51 type powder resistance measurement system produced byDia Instruments Co., Ltd., a sample was set to a cylindrical cell havinga 4 probe electrode, and its thickness and resistivity values weremeasured in condition where a pressure of 60 MPa was added to thesample, and from those values, volume resistivity was calculated.

Whereas, volume resistivity of the conductive particles or fibers wereas follows.

<Conductive Particle>

“Micropearl” AU215 1.4 × 10⁻³ Ωcm “Micropearl” AU225 1.6 × 10⁻³ Ωcm“Bellpearl” C-2000 2.0 × 10⁻² Ωcm Conductive particle B 5.0 × 10⁻² ΩcmConductive particle C 3.5 × 10⁻² Ωcm Conductive particle D 5.2 × 10⁻²Ωcm Conductive particle E 4.5 × 10⁻⁴ Ωcm Conductive particle F 4.0 ×10⁻² Ωcm Conductive particle G 6.1 × 10⁻⁴ Ωcm “Micropearl” AU215surfacetreated article I 1.4 × 10⁻³ Ωcm “Bellpearl” C-2000surface treatedarticle J 2.0 × 10⁻² Ωcm

<Conductive Fiber>

“Torayca” milled fiber MLD-30 6.6 × 10⁻² Ωcm “Torayca” chopped fiberT008-3 9.3 × 10⁻² Ωcm Conductive fiber A 7.1 × 10⁻³ Ωcm

(5) Determination of Compressive Strength after Impact of FiberReinforced Composite Material

24 plies of unidirectional prepreg were laid-up quasi-isotropically in[+45°/0°/−45°/90°]_(3s) constitution, and molded in an autoclave at atemperature of 180° C. for 2 hours under a pressure of 0.59 MPa and at aheating speed of 1.5° C./min priot to the 2 hour cure, to prepare 25pieces of laminate. From each of these laminates, a sample of length 150mm×width 100 mm was cut out and, in accordance with SACMA SRM 2R-94,compressive strength after impact was determined by adding a drop impactof 6.7 J/mm on its center portion.

(6) Determination of Conductivity of Fiber Reinforced Composite Material

24 plies of unidirectional prepreg were laid-up quasi-isotropically in[+45°/0°/−45°/90°]_(3s) constitution, and molded in an autoclave at atemperature of 180° C. for 2 hours under a pressure of 0.59 MPa and at aheating speed of 1.5° C./min priot to the 2 hour cure, to prepare 25pieces of laminate. From each of these laminates, a sample of length 50mm×width 50 mm was cut out and coated on both sides with a conductivepaste “Dotite” (trademark) D-550 (produced by Fujikura Kasei Co., Ltd.),to prepare a sample. For these samples, by using R6581 digitalmultimeter produced by Advantest Corp., resistivity in laminatedirection was measured by four probe method to obtain a volumeresistivity.

Example 1

By a kneader, 10 parts by weight of PES5003P was compounded anddissolved in 50 parts by weight of “Epikote (trademark)” 825 and 50parts by weight of ELM434, and then 19.98 parts by weight of epoxymodified nylon particle A and 0.02 parts by weight of “Micropearl(trademark)” AU215 were kneaded, and furthermore, 40 parts by weight of4,4′-diaminodiphenyl sulfone which is a hardener was kneaded, to preparea thermosetting resin composition.

The prepared thermosetting resin composition was coated on a releasepaper by using a knife coater, to prepare 2 sheets of resin film of 52g/m². Next, on carbon fiber (T800S-24K-10E) arranged into aunidirectional sheet, 2 sheets of the resin film prepared in theabove-mentioned were superposed on both sides of the carbon fiber, andimpregnated with the resin by heat and pressure, to prepare aunidirectional prepreg of which carbon fiber areal weight was 190 g/m²and weight ratio of matrix resin was 35.4%.

By using the prepared unidirectional prepreg, containing ratio ofparticle present in 20% depth range of prepreg thickness, compressivestrength after impact and conductivity of the fiber reinforced compositematerial were determined. The obtained results are shown in Table 1.

Examples 2 to 24 and Comparative Examples 1 to 7

Prepreg were prepared in the same way as Example 1 except changing thekinds of carbon fiber, thermoplastic resin particle or conductiveparticle or the compounding amounts as shown in Tables 1 to 4. By usingthe prepared unidirectional prepreg, containing ratio of particlepresent in 20% depth range of prepreg thickness, compressive strengthafter impact and conductivity of the fiber reinforced composite materialwere determined.

Example 25

By a kneader, after 10 parts by weight of PES5003P was compounded anddissolved in 50 parts by weight of “Epikote (trademark)” 825 and 50parts by weight of ELM434, and furthermore, 40 parts by weight of4,4′-diaminodiphenyl sulfone which is a hardener was kneaded, to preparea thermosetting resin composition. This matrix resin was taken asprimary resin.

By a kneader, 10 parts by weight of PES5003P was compounded anddissolved in 50 parts by weight of “Epikote (trademark)” 825 and 50parts by weight of ELM434, and then, 62.5 parts by weight of epoxymodified nylon particle A and 1.3 parts by weight of “Micropearl(trademark)” AU215 were kneaded, and furthermore, 40 parts by weight of4,4′-diaminodiphenyl sulfone which is a hardener was kneaded, to preparea thermosetting resin composition. This matrix resin was taken assecondary resin.

The prepared primary resin was coated on a release paper by using aknife coater, to prepare 2 sheets of resin film of 31.5 g/m². Next, oncarbon fiber (T800S-24K-10E) arranged into a unidirectional sheet, 2sheets of the resin film prepared in the above-mentioned were superposedon both sides of the carbon fiber, and impregnated with the resin byheat and pressure, to prepare a unidirectional prepreg of which carbonfiber areal weight was 190 g/m² and weight ratio of matrix resin was24.9%.

Next, the prepared secondary resin was coated on a release paper byusing a knife coater, to prepare 2 sheets of resin film of 20.5 g/m².Next, between these secondary resin films facing each other, the aboveprepared primary impregnate prepreg was inserted, and impregnated withthe resin by heat and pressure in the same way as the primary impregnateprepreg, to prepare a secondary impregnate prepreg. This prepreg ofwhich carbon fiber areal weight was 190 g/m² and weight ratio of matrixresin was 35.4% was prepared as a secondary impregnate prepreg. Matrixresin composition of this secondary impregnate prepreg is shown in Table4.

By using the prepared secondary impregnate prepreg, containing ratio ofparticle present in 20% depth range of prepreg thickness, compressivestrength after impact and conductivity of the fiber reinforced compositematerial were determined. The obtained results are shown in Table 4.

Example 26

By a kneader, 10 parts by weight of PES5003P was compounded anddissolved in 50 parts by weight of “Epikote (trademark)” 825 and 50parts by weight of ELM434, and then 40 parts by weight of4,4′-diaminodiphenyl sulfone which is a hardener was kneaded, to preparea thermosetting resin composition.

The prepared thermosetting resin composition was coated on a releasepaper by using a knife coater, to prepare 2 sheets of resin film of 45g/m². Next, on carbon fiber (T800S-24K-10E) arranged into aunidirectional sheet, 2 sheets of the resin film prepared in theabove-mentioned were superposed on both sides of the carbon fiber, andimpregnated with the resin by heat and pressure. Furthermore, on bothsides thereof, TR-55 short fiber which is a thermoplastic resin fiberand “Torayca” milled fiber MLD-30 which is a conductive fiber werescattered. The scattered amounts were 6.5 g/m² and 0.5 g/m²,respectively. In this way, a unidirectional prepreg of which carbonfiber areal weight was 190 g/m² and weight ratio of matrix resin was35.4% was prepared.

By using the prepared unidirectional prepreg, containing ratio ofparticle present in 20% depth range of prepreg thickness, compressivestrength after impact and conductivity of the fiber reinforced compositematerial were determined. The obtained results are shown in Table 5.

Examples 27 to 29

Prepregs were prepared in the same way as Example 25 except changing thekinds of conductive particle or fiber as shown in Tables 5 and changingthe scattered amount of the thermoplastic resin particle or fiber to 6.5g/m², and the scattered amount of the conductive particle or fiber to0.5 g/m². By using the prepared unidirectional prepreg, containing ratioof particle present in 20% depth range of prepreg thickness, compressivestrength after impact and conductivity of the fiber reinforced compositematerial were determined.

Example 30, Comparative examples 8 and 9

Prepregs were prepared in the same way as Example 25 except changing thekinds of thermoplastic resin fiber or conductive fiber as shown inTables 5 and changing the scattered amount of those to 7.0 g/m². Byusing the prepared unidirectional prepreg, containing ratio of theabove-mentioned particle or fiber in 20% depth range of prepregthickness, compressive strength after impact and conductivity of thefiber reinforced composite material were determined.

The obtained results are summarized in Tables 1 to 5.

TABLE 1 Example 1 2 3 4 5 6 Carbon fiber T800S T800S T800S T800S T800ST800S Thermosetting Thermosetting resin resin Composition Epikote 825 5050 50 50 50 50 ELM434 50 50 50 50 50 50 4,4′-diaminodiphenyl sulfone 4040 40 40 40 40 PES5003P 10 10 10 10 10 10 Thermoplastic resin particleSP-10 0 0 0 0 0 0 Epoxy modified nylon particle A 19.98 19.8 19.6 18 1510 Conductive particle “Micropearl” AU215 0.02 0.2 0.4 2 5 10“Micropearl” AU225 0 0 0 0 0 0 “Bellpearl” C-2000 0 0 0 0 0 0 Conductiveparticle B 0 0 0 0 0 0 Conductive particle C 0 0 0 0 0 0 Conductiveparticle D 0 0 0 0 0 0 Conductive particle E 0 0 0 0 0 0 Conductiveparticle F 0 0 0 0 0 0 Conductive particle G 0 0 0 0 0 0 Surface treatedarticle I of “Micropearl” AU215 0 0 0 0 0 0 Surface treated article J of“Bellpearl” C-2000 0 0 0 0 0 0 Compounding amount of [C] (pts by wt)/999.0 99.0 49.0 9.0 3.0 1.0 compounding amount of [D] (pts by wt)Characteristics of prepreg Containing ratio of particle present in 20%97 98 97 96 97 100 depth range Characteristics of Compressive strengthafter impact (MPa) 290 288 289 287 280 265 composite material Volumeresistivity (Ωcm) 1.1 × 10⁵ 1.5 × 10⁴ 5.0 × 10³ 4.2 × 10³ 4.0 × 10³ 4.2× 10³

TABLE 2 Example Comparative example 7 1 2 3 4 Carbon fiber T700S T800ST800S T800S T800S Thermosetting Thermosetting resin resin compositionEpikote 825 50 50 50 50 50 ELM434 50 50 50 50 50 4,4′-diaminodiphenylsulfone 40 40 40 40 40 PES5003P 10 10 10 10 10 Thermoplastic resinparticle SP-10 0 0 0 0 0 Epoxy modified nylon particle A 19.6 20 0 19.998 Conductive particle “Micropearl” AU215 0.4 0 20 0.01 12 “Micropearl”AU225 0 0 0 0 0 “Bellpearl” C-2000 0 0 0 0 0 Conductive particle B 0 0 00 0 Conductive particle C 0 0 0 0 0 Conductive particle D 0 0 0 0 0Conductive particle E 0 0 0 0 0 Conductive particle F 0 0 0 0 0Conductive particle G 0 0 0 0 0 Surface treated article I of“Micropearl” AU215 0 0 0 0 0 Surface treated article J of “Bellpearl”C-2000 0 0 0 0 0 Compounding amount of [C] (pts by wt)/ 9.0 — — 1999.00.7 compounding amount of [D] (pts by wt) Characteristics of prepregContaining ratio of particle present in 20% 97 97 97 97 96 depth rangeCharacteristics of Compressive strength after impact (MPa) 287 289 235289 219 composite material Volume resistivity (Ωcm) 5.7 × 10³ 1.5 × 10⁶3.8 × 10³ 1.1 × 10⁶ 4.2 × 10³

TABLE 3 Example Comparative example 8 9 10 11 12 13 5 6 7 Carbon fiberT800S T800S T800S T800S T800S T800S T800S T800S T800S ThermosettingThermosetting resin resin composition Epikote 825 50 50 50 50 50 50 5050 50 ELM434 50 50 50 50 50 50 50 50 50 4,4′-diaminodiphenyl 40 40 40 4040 40 40 40 40 sulfone PES5003P 10 10 10 10 10 10 10 10 10 Thermoplasticresin particle SP-10 19.98 19.8 19.6 18 15 10 20 19.99 8 Epoxy modified0 0 0 0 0 0 0 0 0 nylon particle A Conductive particle “Micropearl”AU215 0.02 0.2 0.4 2 5 10 0 0.01 12 “Micropearl” AU225 0 0 0 0 0 0 0 0 0“Bellpearl” C-2000 0 0 0 0 0 0 0 0 0 Conductive particle B 0 0 0 0 0 0 00 0 Conductive particle C 0 0 0 0 0 0 0 0 0 Conductive particle D 0 0 00 0 0 0 0 0 Conductive particle E 0 0 0 0 0 0 0 0 0 Conductive particleF 0 0 0 0 0 0 0 0 0 Conductive particle G 0 0 0 0 0 0 0 0 0 Surfacetreated article 0 0 0 0 0 0 0 0 0 I of “Micropearl” AU215 Surfacetreated 0 0 0 0 0 0 0 0 0 article J of “Bellpearl” C-2000 Compoundingamount 999.0 99.0 49.0 9.0 3.0 1.0 — 1999.0 0.7 of [C] (pts by wt)/compounding amount of [D] (pts by wt) Characteristics of Containingratio 96 97 97 98 96 97 97 98 97 Prepreg of particle present in 20%depth range Characteristics of Compressive strength 345 343 343 335 328298 343 344 258 Composite after impact (MPa) material Volume resistivity9.8 × 10⁴ 1.3 × 10⁴ 4.8 × 10³ 4.0 × 10³ 3.9 × 10³ 3.8 × 10³ 1.4 × 10⁶1.0 × 10⁶ 3.8 × 10³ (Ωcm)

TABLE 4 Example 14 15 16 17 18 19 Carbon fiber T800S T800S T800S T800ST800S T800S Thermosetting Thermosetting resin resin Epikote 825 50 50 5050 50 50 composition ELM434 50 50 50 50 50 50 4,4′-diaminodiphenylsulfone 40 40 40 40 40 40 PES5003P 10 10 10 10 10 10 Thermoplastic resinparticle SP-10 0 0 0 0 0 0 Epoxy modified nylon particle A 19.6 19.619.6 19.6 19.6 19.6 Conductive particle “Micropearl” AU215 0 0 0 0 0 0“Micropearl” AU225 0 0 0 0 0 0 “Bellpearl” C-2000 0.4 0 0 0 0 0Conductive particle B 0 0.4 0 0 0 0 Conductive particle C 0 0 0.4 0 0 0Conductive particle D 0 0 0 0.4 0 0 Conductive particle E 0 0 0 0 0.4 0Conductive particle F 0 0 0 0 0 0.4 Conductive particle G 0 0 0 0 0 0Surface treated article I of “Micropearl” 0 0 0 0 0 0 AU215 Surfacetreated article J of “Bellpearl” C-2000 0 0 0 0 0 0 Compounding amountof [C] (pts by wt)/ 49.0 49.0 49.0 49.0 49.0 49.0 compounding amount of[D] (pts by wt) Characteristics Containing ratio of particle present in20% 96 97 98 97 98 98 of prepreg depth range Characteristics Compressivestrength after impact (MPa) 285 290 301 297 303 291 of composite Volumeresistivity (Ωcm) 2.8 × 10³ 3.7 × 10⁴ 1.1 × 10⁴ 3.5 × 10⁴ 4.8 × 10³ 2.2× 10⁴ material Example 20 21 22 23 24 25 Carbon fiber T800S T800S T800ST800S T800S T800S Thermosetting Thermosetting resin resin Epikote 825 5050 50 50 50 50 composition ELM434 50 50 50 50 50 50 4,4′-diaminodiphenylsulfone 40 40 40 40 40 40 PES5003P 10 10 10 10 10 10 Thermoplastic resinparticle SP-10 0 0 0 0 0 0 Epoxy modified nylon particle A 19.6 19.6 0 019.6 19.6 Conductive particle “Micropearl” AU215 0 0 0 0 0 0.4“Micropearl” AU225 0 0 0 0 0.4 0 “Bellpearl” C-2000 0 0 0 0 0 0Conductive particle B 0 0 0 0 0 0 Conductive particle C 0 0 0 0 0 0Conductive particle D 0 0 0 0 0 0 Conductive particle E 0 0 20 0 0 0Conductive particle F 0 0 0 0 0 0 Conductive particle G 0 0 0 20 0 0Surface treated article I of “Micropearl” 0.4 0 0 0 0 0 AU215 Surfacetreated article J of “Bellpearl” C-2000 0 0.4 0 0 0 0 Compounding amountof [C] (pts by wt)/ 49.0 49.0 — — 49.0 49.0 compounding amount of [D](pts by wt) Characteristics Containing ratio of particle present in 20%97 97 97 97 98 99 of prepreg depth range Characteristics Compressivestrength after impact (MPa) 299 296 294 267 290 308 of composite Volumeresistivity (Ωcm) 5.3 × 10³ 2.6 × 10³ 2.7 × 10³ 3.3 × 10³ 2.1 × 10³ 2.0× 10³ material

TABLE 5 Example Comparative example 26 27 29 30 8 9 Carbon fiber T800ST800S T800S T800S T800S T800S T800S Thermosetting Thermosetting resinresin composition Epikote 825 50 50 50 50 50 50 50 ELM434 50 50 50 50 5050 50 4,4′-diaminodiphenyl sulfone 40 40 40 40 40 40 40 PES5003P 10 1010 10 10 10 10 Thermoplastic resin fiber TR-55 TR-55 — TR-55 — TR-55 —short fiber short fiber short fiber short fiber Thermoplastic resinparticle — — SP-10 — — — — Conductive fiber MLD-30 T008-3 MLD-30 —Conductive — MLD-30 fiber A Conductive particle — — — Conductive — — —particle E Compounding amount of [C] (pts by wt)/ 13.0 13.0 13.0 13.0 —— — compounding amount of [D] (pts by wt) Characteristics of Containingratio of particle present in 97 97 98 96 96 97 98 prepreg 20% depthrange Characteristics of Compressive strength after impact (MPa) 271 269283 273 268 273 207 Composite Volume resistivity value (Ωcm) 4.1 × 10⁴4.7 × 10⁴ 8.3 × 10³ 3.9 × 10³ 9.1 × 10³ 1.8 × 10⁶ 5.3 × 10³ material

By comparison between Examples 1 to 6 and Comparative examples 1 to 4,it is found that the carbon fiber reinforced composite material of thepresent invention peculiarly realizes a high compressive strength afterimpact and a low volume resistivity, and satisfies a high level impactresistance and conductivity together. And, a relation between theseresults and the scope of claim of the present invention is summarized inFIG. 2. In FIG. 2, the weight ratio expressed by the [compounding amountof thermoplastic resin particle (parts by weight)]/[compounding amountof conductive particle (parts by weight)] is shown in the horizontalline and, “◯” denotes the value of compressive strength after impactshown in the left vertical line and “▴” denotes the volume resistivityshown in the right vertical line. Usually, when the weight ratioexpressed by the [compounding amount of thermoplastic resin particle(parts by weight)]/[compounding amount of conductive particle (parts byweight)] is large, an impact resistance is excellent, but a volumeresistivity also becomes large, and when the weight ratio expressed bythe [compounding amount of thermoplastic resin particle (parts byweight)]/[compounding amount of conductive particle (parts by weight)]is small, a volume resistivity is small, but an impact resistance ispoor. It is found that, in the present invention, the scope of claim 1is a scope where a low volume resistivity and a high compressivestrength after impact can be achieved, and it is the range whereconductivity and impact resistance can be compatible.

As to these results, the same can be said by comparison between Examples7 to 30 and Comparative examples 5 to 9. Furthermore, by comparisonbetween Example 3 and Example 7, it is found that Example 3 in whichT800S-24K-10E which is a carbon fiber having a tensile modulus of 290GPa was used is more excellent compared to Example 7 in whichT700S-24K-50C which is a carbon fiber having a tensile modulus of 230GPa was used. And, as shown in Examples 14 to 30, in the presentinvention, various combination of thermoplastic resin particle or fiberand conductive particle or fiber can be used.

It is found that, compared to Examples 3 and 14, surface treatedarticles of conductive particle as shown in Examples 20 and 21 canrealize a strong adhesion with the thermosetting resin, and has achieveda higher compressive strength after impact.

Furthermore, in Examples 22, 23, without using a thermoplastic resinparticle, by using the conductive particle E or G only of whichthermoplastic resin nucleus is coated with a conductive substance, or inExample 30, too, without using a thermoplastic resin fiber, by using theconductive fiber A only of which core of thermoplastic resin is coatedwith the conductive substance, a low volume resistivity and a highcompressive strength after impact can be achieved, and it is found thatconductivity and impact resistance can be compatible. And, when theconductive particles E and G of Examples 22 and 23 are compared, it isfound that the conductive particle E having a higher G₁ has achieved ahigher compressive strength after impact.

In Example 25 in which the secondary impregnate prepreg was used, thecontaining ratio of particle present in 20% depth is higher than Example3, and it is found that a higher conductivity and impact resistance canbe obtained.

INDUSTRIAL APPLICABILITY

The prepreg and the carbon fiber reinforced composite material of thepresent invention has an excellent impact resistance and conductivitytogether, and can be widely applied to an aircraft structural member, ablade of windmill, an automotive outer panel and computer applicationssuch as an IC tray or a kyotai (housing) of notebook computer, etc., andit is useful.

1. A prepreg comprising: a carbon fiber A; a thermosetting resin B;thermoplastic resin particles C; and conductive particles D, wherein aweight ratio expressed by C content (parts by weight)/D content (partsby weight) is 1 to 1000, and wherein 90 to 100 wt % of each of thethermoplastic resin particles C and the conductive particles D islocalized to be within a 20% depth range from one surface of the prepregin a thickness direction.
 2. A prepreg according to claim 1, wherein anaverage particle diameter of the conductive particles D is at most 150μm and is equal to or larger than an average particle diameter of thethermoplastic resin particles C.
 3. A prepreg according to claim 1,wherein the conductive particles D are at least one type selected fromthe group consisting of carbon particles, particles having a nucleus ofinorganic material that is coated with a conductive substance, andparticles having a nucleus of organic material that is coated with aconductive substance.
 4. A prepreg according to claim 1, wherein theconductive particles D have a volume resistivity of 10 to 10⁻⁹ Ωcm.
 5. Aprepreg according to claim 1, wherein a total weight of thethermoplastic resin particles C and the conductive particles D is 1 to20 wt % with respect to the prepreg.
 6. A prepreg according to claim 1,wherein the carbon fiber has a tensile modulus of 260 to 400 GPa.
 7. Acarbon fiber reinforced composite material produced by curing theprepreg according to any one of claims 1 to 6.